Re: perf probe line numbers + CONFIG_DEBUG_INFO_SPLIT=y

From: Masami Hiramatsu
Date: Tue Apr 17 2018 - 23:23:55 EST

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In reply to: Arnaldo Carvalho de Melo: "perf probe line numbers + CONFIG_DEBUG_INFO_SPLIT=y"
Next in thread: Masami Hiramatsu: "Re: perf probe line numbers + CONFIG_DEBUG_INFO_SPLIT=y"
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Hi Arnaldo,

On Tue, 17 Apr 2018 14:47:01 -0300
Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:

> Hi Masami,
>
> I just tried building the kernel using:
>
> CONFIG_DEBUG_INFO=y
> # CONFIG_DEBUG_INFO_REDUCED is not set
> CONFIG_DEBUG_INFO_SPLIT=y
> # CONFIG_DEBUG_INFO_DWARF4 is not set

Yeah, this is what I have to solve...

>
> that info split looked interesting, and I thought that since we
> use elfutils we'd get that for free somehow, so I tried getname_flags
> and got the output at the end of this message, with these artifacts:
>
> 1) the function signature doesn't appear at the start of the '-L
> getname_flags' output
>
> 2) offsets are not calculated, just the line numbers in fs/namei.c (it
> matches the first line :130 with the first line number.

I think we need to use elfutils with different way, maybe passing
correct debuginfo file, instead of vmlinux.
Oh, did you got the source code lines? I'll try to reproduce it.

> And then if I try adding a probe at some places, say line 202, to
> collect the filename being brought from userspace to the kernel, it
> fails:
>
> [root@jouet perf]# perf probe "vfs_getname=getname_flags:202 pathname=result->name:string"
> Probe point 'getname_flags:202' not found.
> Error: Failed to add events.
> [root@jouet perf]#
>
> If I just try putting the probe without renaming nor collecting vars, to
> have a simpler probe request:
>
> [root@jouet perf]# perf probe getname_flags:202
> Probe point 'getname_flags:202' not found.
> Error: Failed to add events.
> [root@jouet perf]#
>
> Or even:
>
> [root@jouet perf]# perf probe getname_flags
> Failed to find scope of probe point.
> getname_flags is out of .text, skip it.
> Error: Failed to add events.
> [root@jouet perf]#
>
> [root@jouet perf]# grep getname_flags /proc/kallsyms
> ffffffffb329a5a0 T getname_flags
> [root@jouet perf]#
>
> I'll try with CONFIG_DEBUG_INFO_SPLIT not set, but have you ever got
> such a report?

No, but I noticed. I will take a look and fix it.

Thanks,

>
> - Arnaldo
>
> # perf probe -L getname_flags
> </home/acme/git/linux/fs/namei.c:130>
> 130 {
> struct filename *result;
> char *kname;
> int len;
> BUILD_BUG_ON(offsetof(struct filename, iname) % sizeof(long) != 0);
>
> result = audit_reusename(filename);
> 137 if (result)
> return result;
>
> 140 result = __getname();
> 141 if (unlikely(!result))
> 142 return ERR_PTR(-ENOMEM);
>
> /*
> * First, try to embed the struct filename inside the names_cache
> * allocation
> */
> 148 kname = (char *)result->iname;
> 149 result->name = kname;
>
> 151 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
> 152 if (unlikely(len < 0)) {
> 153 __putname(result);
> 154 return ERR_PTR(len);
> }
>
> /*
> * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
> * separate struct filename so we can dedicate the entire
> * names_cache allocation for the pathname, and re-do the copy from
> * userland.
> */
> 163 if (unlikely(len == EMBEDDED_NAME_MAX)) {
> const size_t size = offsetof(struct filename, iname[1]);
> kname = (char *)result;
>
> /*
> * size is chosen that way we to guarantee that
> * result->iname[0] is within the same object and that
> * kname can't be equal to result->iname, no matter what.
> */
> result = kzalloc(size, GFP_KERNEL);
> 173 if (unlikely(!result)) {
> 174 __putname(kname);
> 175 return ERR_PTR(-ENOMEM);
> }
> 177 result->name = kname;
> 178 len = strncpy_from_user(kname, filename, PATH_MAX);
> 179 if (unlikely(len < 0)) {
> 180 __putname(kname);
> 181 kfree(result);
> 182 return ERR_PTR(len);
> }
> 184 if (unlikely(len == PATH_MAX)) {
> 185 __putname(kname);
> 186 kfree(result);
> 187 return ERR_PTR(-ENAMETOOLONG);
> }
> }
>
> 191 result->refcnt = 1;
> /* The empty path is special. */
> 193 if (unlikely(!len)) {
> 194 if (empty)
> 195 *empty = 1;
> 196 if (!(flags & LOOKUP_EMPTY)) {
> 197 putname(result);
> 198 return ERR_PTR(-ENOENT);
> }
> }
>
> 202 result->uptr = filename;
> 203 result->aname = NULL;
> audit_getname(result);
> return result;
> 206 }
>
> struct filename *
> getname(const char __user * filename)
> 210 {
> 211 return getname_flags(filename, 0, NULL);
> }
>
> struct filename *
> getname_kernel(const char * filename)
> 216 {
> struct filename *result;
> 218 int len = strlen(filename) + 1;
>
> 220 result = __getname();
> 221 if (unlikely(!result))
> 222 return ERR_PTR(-ENOMEM);
>
> 224 if (len <= EMBEDDED_NAME_MAX) {
> 225 result->name = (char *)result->iname;
> 226 } else if (len <= PATH_MAX) {
> const size_t size = offsetof(struct filename, iname[1]);
> struct filename *tmp;
>
> tmp = kmalloc(size, GFP_KERNEL);
> 231 if (unlikely(!tmp)) {
> 232 __putname(result);
> 233 return ERR_PTR(-ENOMEM);
> }
> 235 tmp->name = (char *)result;
> result = tmp;
> } else {
> 238 __putname(result);
> 239 return ERR_PTR(-ENAMETOOLONG);
> }
> 241 memcpy((char *)result->name, filename, len);
> 242 result->uptr = NULL;
> 243 result->aname = NULL;
> 244 result->refcnt = 1;
> audit_getname(result);
>
> return result;
> 248 }
>
> void putname(struct filename *name)
> 251 {
> 252 BUG_ON(name->refcnt <= 0);
>
> 254 if (--name->refcnt > 0)
> return;
>
> 257 if (name->name != name->iname) {
> 258 __putname(name->name);
> 259 kfree(name);
> } else
> 261 __putname(name);
> 262 }
>
> static int check_acl(struct inode *inode, int mask)
> {
> #ifdef CONFIG_FS_POSIX_ACL
> struct posix_acl *acl;
>
> 269 if (mask & MAY_NOT_BLOCK) {
> 270 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
> 271 if (!acl)
> return -EAGAIN;
> /* no ->get_acl() calls in RCU mode... */
> 274 if (is_uncached_acl(acl))
> 275 return -ECHILD;
> 276 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
> }
>
> 279 acl = get_acl(inode, ACL_TYPE_ACCESS);
> 280 if (IS_ERR(acl))
> return PTR_ERR(acl);
> 282 if (acl) {
> 283 int error = posix_acl_permission(inode, acl, mask);
> posix_acl_release(acl);
> return error;
> }
> #endif
>
> return -EAGAIN;
> }
>
> /*
> * This does the basic permission checking
> */
> static int acl_permission_check(struct inode *inode, int mask)
> {
> 297 unsigned int mode = inode->i_mode;
>
> 299 if (likely(uid_eq(current_fsuid(), inode->i_uid)))
> 300 mode >>= 6;
> else {
> 302 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
> int error = check_acl(inode, mask);
> 304 if (error != -EAGAIN)
> return error;
> }
>
> 308 if (in_group_p(inode->i_gid))
> 309 mode >>= 3;
> }
>
> /*
> * If the DACs are ok we don't need any capability check.
> */
> 315 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
> 316 return 0;
> return -EACCES;
> }
>
> /**
> * generic_permission - check for access rights on a Posix-like filesystem
> * @inode: inode to check access rights for
> * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
> *
> * Used to check for read/write/execute permissions on a file.
> * We use "fsuid" for this, letting us set arbitrary permissions
> * for filesystem access without changing the "normal" uids which
> * are used for other things.
> *
> * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
> * request cannot be satisfied (eg. requires blocking or too much complexity).
> * It would then be called again in ref-walk mode.
> */
> int generic_permission(struct inode *inode, int mask)
> 335 {
> int ret;
>
> /*
> * Do the basic permission checks.
> */
> ret = acl_permission_check(inode, mask);
> 342 if (ret != -EACCES)
> return ret;
>
> 345 if (S_ISDIR(inode->i_mode)) {
> /* DACs are overridable for directories */
> 347 if (!(mask & MAY_WRITE))
> 348 if (capable_wrt_inode_uidgid(inode,
> CAP_DAC_READ_SEARCH))
> return 0;
> if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
> return 0;
> 353 return -EACCES;
> }
>
> /*
> * Searching includes executable on directories, else just read.
> */
> 359 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
> 360 if (mask == MAY_READ)
> 361 if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
> return 0;
> /*
> * Read/write DACs are always overridable.
> * Executable DACs are overridable when there is
> * at least one exec bit set.
> */
> 368 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
> 369 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
> return 0;
>
> return -EACCES;
> 373 }
> EXPORT_SYMBOL(generic_permission);
>
> /*
> * We _really_ want to just do "generic_permission()" without
> * even looking at the inode->i_op values. So we keep a cache
> * flag in inode->i_opflags, that says "this has not special
> * permission function, use the fast case".
> */
> static inline int do_inode_permission(struct inode *inode, int mask)
> {
> 384 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
> 385 if (likely(inode->i_op->permission))
> 386 return inode->i_op->permission(inode, mask);
>
> /* This gets set once for the inode lifetime */
> spin_lock(&inode->i_lock);
> 390 inode->i_opflags |= IOP_FASTPERM;
> spin_unlock(&inode->i_lock);
> }
> 393 return generic_permission(inode, mask);
> }
>
> /**
> * sb_permission - Check superblock-level permissions
> * @sb: Superblock of inode to check permission on
> * @inode: Inode to check permission on
> * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
> *
> * Separate out file-system wide checks from inode-specific permission checks.
> */
> static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
> {
> 406 if (unlikely(mask & MAY_WRITE)) {
> 407 umode_t mode = inode->i_mode;
>
> /* Nobody gets write access to a read-only fs. */
> 410 if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
> return -EROFS;
> }
> return 0;
> }
>
> /**
> * inode_permission - Check for access rights to a given inode
> * @inode: Inode to check permission on
> * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
> *
> * Check for read/write/execute permissions on an inode. We use fs[ug]id for
> * this, letting us set arbitrary permissions for filesystem access without
> * changing the "normal" UIDs which are used for other things.
> *
> * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
> */
> int inode_permission(struct inode *inode, int mask)
> 428 {
> int retval;
>
> retval = sb_permission(inode->i_sb, inode, mask);
> if (retval)
> return retval;
>
> if (unlikely(mask & MAY_WRITE)) {
> /*
> * Nobody gets write access to an immutable file.
> */
> 439 if (IS_IMMUTABLE(inode))
> 440 return -EPERM;
>
> /*
> * Updating mtime will likely cause i_uid and i_gid to be
> * written back improperly if their true value is unknown
> * to the vfs.
> */
> if (HAS_UNMAPPED_ID(inode))
> 448 return -EACCES;
> }
>
> retval = do_inode_permission(inode, mask);
> 452 if (retval)
> return retval;
>
> 455 retval = devcgroup_inode_permission(inode, mask);
> 456 if (retval)
> return retval;
>
> 459 return security_inode_permission(inode, mask);
> 460 }
> EXPORT_SYMBOL(inode_permission);
>
> /**
> * path_get - get a reference to a path
> * @path: path to get the reference to
> *
> * Given a path increment the reference count to the dentry and the vfsmount.
> */
> void path_get(const struct path *path)
> 470 {
> 471 mntget(path->mnt);
> 472 dget(path->dentry);
> 473 }
> EXPORT_SYMBOL(path_get);
>
> /**
> * path_put - put a reference to a path
> * @path: path to put the reference to
> *
> * Given a path decrement the reference count to the dentry and the vfsmount.
> */
> void path_put(const struct path *path)
> 483 {
> 484 dput(path->dentry);
> 485 mntput(path->mnt);
> 486 }
> EXPORT_SYMBOL(path_put);
>
> #define EMBEDDED_LEVELS 2
> struct nameidata {
> struct path path;
> struct qstr last;
> struct path root;
> struct inode *inode; /* path.dentry.d_inode */
> unsigned int flags;
> unsigned seq, m_seq;
> int last_type;
> unsigned depth;
> int total_link_count;
> struct saved {
> struct path link;
> struct delayed_call done;
> const char *name;
> unsigned seq;
> } *stack, internal[EMBEDDED_LEVELS];
> struct filename *name;
> struct nameidata *saved;
> struct inode *link_inode;
> unsigned root_seq;
> int dfd;
> } __randomize_layout;
>
> static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
> {
> 515 struct nameidata *old = current->nameidata;
> 516 p->stack = p->internal;
> 517 p->dfd = dfd;
> 518 p->name = name;
> 519 p->total_link_count = old ? old->total_link_count : 0;
> 520 p->saved = old;
> 521 current->nameidata = p;
> }
>
> static void restore_nameidata(void)
> 525 {
> 526 struct nameidata *now = current->nameidata, *old = now->saved;
>
> 528 current->nameidata = old;
> 529 if (old)
> 530 old->total_link_count = now->total_link_count;
> 531 if (now->stack != now->internal)
> 532 kfree(now->stack);
> 533 }
>
> static int __nd_alloc_stack(struct nameidata *nd)
> 536 {
> struct saved *p;
>
> 539 if (nd->flags & LOOKUP_RCU) {
> p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
> GFP_ATOMIC);
> 542 if (unlikely(!p))
> 543 return -ECHILD;
> } else {
> p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
> GFP_KERNEL);
> 547 if (unlikely(!p))
> 548 return -ENOMEM;
> }
> 550 memcpy(p, nd->internal, sizeof(nd->internal));
> 551 nd->stack = p;
> 552 return 0;
> 553 }
>
> /**
> * path_connected - Verify that a path->dentry is below path->mnt.mnt_root
> * @path: nameidate to verify
> *
> * Rename can sometimes move a file or directory outside of a bind
> * mount, path_connected allows those cases to be detected.
> */
> static bool path_connected(const struct path *path)
> 563 {
> 564 struct vfsmount *mnt = path->mnt;
> 565 struct super_block *sb = mnt->mnt_sb;
>
> /* Bind mounts and multi-root filesystems can have disconnected paths */
> 568 if (!(sb->s_iflags & SB_I_MULTIROOT) && (mnt->mnt_root == sb->s_root))
> return true;
>
> 571 return is_subdir(path->dentry, mnt->mnt_root);
> 572 }
>
> static inline int nd_alloc_stack(struct nameidata *nd)
> {
> 576 if (likely(nd->depth != EMBEDDED_LEVELS))
> return 0;
> 578 if (likely(nd->stack != nd->internal))
> return 0;
> 580 return __nd_alloc_stack(nd);
> }
>
> static void drop_links(struct nameidata *nd)
> {
> 585 int i = nd->depth;
> 586 while (i--) {
> 587 struct saved *last = nd->stack + i;
> do_delayed_call(&last->done);
> clear_delayed_call(&last->done);
> }
> }
>
> static void terminate_walk(struct nameidata *nd)
> 594 {
> drop_links(nd);
> 596 if (!(nd->flags & LOOKUP_RCU)) {
> int i;
> path_put(&nd->path);
> 599 for (i = 0; i < nd->depth; i++)
> 600 path_put(&nd->stack[i].link);
> 601 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
> path_put(&nd->root);
> 603 nd->root.mnt = NULL;
> }
> } else {
> 606 nd->flags &= ~LOOKUP_RCU;
> 607 if (!(nd->flags & LOOKUP_ROOT))
> 608 nd->root.mnt = NULL;
> rcu_read_unlock();
> }
> 611 nd->depth = 0;
> 612 }
>
> /* path_put is needed afterwards regardless of success or failure */
> 615 static bool legitimize_path(struct nameidata *nd,
> struct path *path, unsigned seq)
> {
> 618 int res = __legitimize_mnt(path->mnt, nd->m_seq);
> 619 if (unlikely(res)) {
> 620 if (res > 0)
> 621 path->mnt = NULL;
> 622 path->dentry = NULL;
> 623 return false;
> }
> 625 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
> path->dentry = NULL;
> return false;
> }
> 629 return !read_seqcount_retry(&path->dentry->d_seq, seq);
> 630 }
>
> static bool legitimize_links(struct nameidata *nd)
> 633 {
> int i;
> 635 for (i = 0; i < nd->depth; i++) {
> 636 struct saved *last = nd->stack + i;
> 637 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
> drop_links(nd);
> 639 nd->depth = i + 1;
> 640 return false;
> }
> }
> 643 return true;
> 644 }
>
> /*
> * Path walking has 2 modes, rcu-walk and ref-walk (see
> * Documentation/filesystems/path-lookup.txt). In situations when we can't
> * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
> * normal reference counts on dentries and vfsmounts to transition to ref-walk
> * mode. Refcounts are grabbed at the last known good point before rcu-walk
> * got stuck, so ref-walk may continue from there. If this is not successful
> * (eg. a seqcount has changed), then failure is returned and it's up to caller
> * to restart the path walk from the beginning in ref-walk mode.
> */
>
> /**
> * unlazy_walk - try to switch to ref-walk mode.
> * @nd: nameidata pathwalk data
> * Returns: 0 on success, -ECHILD on failure
> *
> * unlazy_walk attempts to legitimize the current nd->path and nd->root
> * for ref-walk mode.
> * Must be called from rcu-walk context.
> * Nothing should touch nameidata between unlazy_walk() failure and
> * terminate_walk().
> */
> static int unlazy_walk(struct nameidata *nd)
> 669 {
> 670 struct dentry *parent = nd->path.dentry;
>
> 672 BUG_ON(!(nd->flags & LOOKUP_RCU));
>
> 674 nd->flags &= ~LOOKUP_RCU;
> 675 if (unlikely(!legitimize_links(nd)))
> goto out2;
> 677 if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
> goto out1;
> 679 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
> 680 if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq)))
> goto out;
> }
> rcu_read_unlock();
> 684 BUG_ON(nd->inode != parent->d_inode);
> 685 return 0;
>
> out2:
> 688 nd->path.mnt = NULL;
> 689 nd->path.dentry = NULL;
> out1:
> 691 if (!(nd->flags & LOOKUP_ROOT))
> 692 nd->root.mnt = NULL;
> out:
> rcu_read_unlock();
> 695 return -ECHILD;
> 696 }
>
> /**
> * unlazy_child - try to switch to ref-walk mode.
> * @nd: nameidata pathwalk data
> * @dentry: child of nd->path.dentry
> * @seq: seq number to check dentry against
> * Returns: 0 on success, -ECHILD on failure
> *
> * unlazy_child attempts to legitimize the current nd->path, nd->root and dentry
> * for ref-walk mode. @dentry must be a path found by a do_lookup call on
> * @nd. Must be called from rcu-walk context.
> * Nothing should touch nameidata between unlazy_child() failure and
> * terminate_walk().
> */
> static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned seq)
> {
> 713 BUG_ON(!(nd->flags & LOOKUP_RCU));
>
> 715 nd->flags &= ~LOOKUP_RCU;
> 716 if (unlikely(!legitimize_links(nd)))
> goto out2;
> 718 if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq)))
> goto out2;
> 720 if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref)))
> goto out1;
>
> /*
> * We need to move both the parent and the dentry from the RCU domain
> * to be properly refcounted. And the sequence number in the dentry
> * validates *both* dentry counters, since we checked the sequence
> * number of the parent after we got the child sequence number. So we
> * know the parent must still be valid if the child sequence number is
> */
> 730 if (unlikely(!lockref_get_not_dead(&dentry->d_lockref)))
> goto out;
> 732 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) {
> rcu_read_unlock();
> 734 dput(dentry);
> goto drop_root_mnt;
> }
> /*
> * Sequence counts matched. Now make sure that the root is
> * still valid and get it if required.
> */
> 741 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
> 742 if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) {
> rcu_read_unlock();
> 744 dput(dentry);
> return -ECHILD;
> }
> }
>
> rcu_read_unlock();
> return 0;
>
> out2:
> 753 nd->path.mnt = NULL;
> out1:
> 755 nd->path.dentry = NULL;
> out:
> rcu_read_unlock();
> drop_root_mnt:
> 759 if (!(nd->flags & LOOKUP_ROOT))
> 760 nd->root.mnt = NULL;
> return -ECHILD;
> }
>
> static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
> {
> 766 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
> 767 return dentry->d_op->d_revalidate(dentry, flags);
> else
> 769 return 1;
> }
>
> /**
> * complete_walk - successful completion of path walk
> * @nd: pointer nameidata
> *
> * If we had been in RCU mode, drop out of it and legitimize nd->path.
> * Revalidate the final result, unless we'd already done that during
> * the path walk or the filesystem doesn't ask for it. Return 0 on
> * success, -error on failure. In case of failure caller does not
> * need to drop nd->path.
> */
> static int complete_walk(struct nameidata *nd)
> 783 {
> 784 struct dentry *dentry = nd->path.dentry;
> int status;
>
> 787 if (nd->flags & LOOKUP_RCU) {
> 788 if (!(nd->flags & LOOKUP_ROOT))
> 789 nd->root.mnt = NULL;
> 790 if (unlikely(unlazy_walk(nd)))
> 791 return -ECHILD;
> }
>
> 794 if (likely(!(nd->flags & LOOKUP_JUMPED)))
> 795 return 0;
>
> 797 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
> return 0;
>
> 800 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
> 801 if (status > 0)
> return 0;
>
> if (!status)
> 805 status = -ESTALE;
>
> return status;
> 808 }
>
> static void set_root(struct nameidata *nd)
> 811 {
> 812 struct fs_struct *fs = current->fs;
>
> 814 if (nd->flags & LOOKUP_RCU) {
> unsigned seq;
>
> do {
> seq = read_seqcount_begin(&fs->seq);
> 819 nd->root = fs->root;
> 820 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
> 821 } while (read_seqcount_retry(&fs->seq, seq));
> } else {
> 823 get_fs_root(fs, &nd->root);
> }
> 825 }
>
> static void path_put_conditional(struct path *path, struct nameidata *nd)
> {
> 829 dput(path->dentry);
> 830 if (path->mnt != nd->path.mnt)
> 831 mntput(path->mnt);
> }
>
> static inline void path_to_nameidata(const struct path *path,
> struct nameidata *nd)
> {
> 837 if (!(nd->flags & LOOKUP_RCU)) {
> 838 dput(nd->path.dentry);
> 839 if (nd->path.mnt != path->mnt)
> 840 mntput(nd->path.mnt);
> }
> 842 nd->path.mnt = path->mnt;
> 843 nd->path.dentry = path->dentry;
> }
>
> static int nd_jump_root(struct nameidata *nd)
> 847 {
> 848 if (nd->flags & LOOKUP_RCU) {
> struct dentry *d;
> 850 nd->path = nd->root;
> 851 d = nd->path.dentry;
> 852 nd->inode = d->d_inode;
> 853 nd->seq = nd->root_seq;
> 854 if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
> 855 return -ECHILD;
> } else {
> path_put(&nd->path);
> 858 nd->path = nd->root;
> 859 path_get(&nd->path);
> 860 nd->inode = nd->path.dentry->d_inode;
> }
> 862 nd->flags |= LOOKUP_JUMPED;
> 863 return 0;
> 864 }
>
> /*
> * Helper to directly jump to a known parsed path from ->get_link,
> * caller must have taken a reference to path beforehand.
> */
> void nd_jump_link(struct path *path)
> 871 {
> 872 struct nameidata *nd = current->nameidata;
> path_put(&nd->path);
>
> 875 nd->path = *path;
> 876 nd->inode = nd->path.dentry->d_inode;
> 877 nd->flags |= LOOKUP_JUMPED;
> 878 }
>
> static inline void put_link(struct nameidata *nd)
> {
> 882 struct saved *last = nd->stack + --nd->depth;
> do_delayed_call(&last->done);
> 884 if (!(nd->flags & LOOKUP_RCU))
> path_put(&last->link);
> }
>
> int sysctl_protected_symlinks __read_mostly = 0;
> int sysctl_protected_hardlinks __read_mostly = 0;
>
> /**
> * may_follow_link - Check symlink following for unsafe situations
> * @nd: nameidata pathwalk data
> *
> * In the case of the sysctl_protected_symlinks sysctl being enabled,
> * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
> * in a sticky world-writable directory. This is to protect privileged
> * processes from failing races against path names that may change out
> * from under them by way of other users creating malicious symlinks.
> * It will permit symlinks to be followed only when outside a sticky
> * world-writable directory, or when the uid of the symlink and follower
> * match, or when the directory owner matches the symlink's owner.
> *
> * Returns 0 if following the symlink is allowed, -ve on error.
> */
> static inline int may_follow_link(struct nameidata *nd)
> {
> const struct inode *inode;
> const struct inode *parent;
> kuid_t puid;
>
> 912 if (!sysctl_protected_symlinks)
> return 0;
>
> /* Allowed if owner and follower match. */
> inode = nd->link_inode;
> 917 if (uid_eq(current_cred()->fsuid, inode->i_uid))
> return 0;
>
> /* Allowed if parent directory not sticky and world-writable. */
> 921 parent = nd->inode;
> 922 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
> return 0;
>
> /* Allowed if parent directory and link owner match. */
> 926 puid = parent->i_uid;
> 927 if (uid_valid(puid) && uid_eq(puid, inode->i_uid))
> return 0;
>
> 930 if (nd->flags & LOOKUP_RCU)
> return -ECHILD;
>
> 933 audit_inode(nd->name, nd->stack[0].link.dentry, 0);
> 934 audit_log_link_denied("follow_link");
> return -EACCES;
> }
>
> /**
> * safe_hardlink_source - Check for safe hardlink conditions
> * @inode: the source inode to hardlink from
> *
> * Return false if at least one of the following conditions:
> * - inode is not a regular file
> * - inode is setuid
> * - inode is setgid and group-exec
> * - access failure for read and write
> *
> * Otherwise returns true.
> */
> static bool safe_hardlink_source(struct inode *inode)
> {
> 952 umode_t mode = inode->i_mode;
>
> /* Special files should not get pinned to the filesystem. */
> 955 if (!S_ISREG(mode))
> return false;
>
> /* Setuid files should not get pinned to the filesystem. */
> 959 if (mode & S_ISUID)
> return false;
>
> /* Executable setgid files should not get pinned to the filesystem. */
> 963 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
> return false;
>
> /* Hardlinking to unreadable or unwritable sources is dangerous. */
> 967 if (inode_permission(inode, MAY_READ | MAY_WRITE))
> return false;
>
> return true;
> }
>
> /**
> * may_linkat - Check permissions for creating a hardlink
> * @link: the source to hardlink from
> *
> * Block hardlink when all of:
> * - sysctl_protected_hardlinks enabled
> * - fsuid does not match inode
> * - hardlink source is unsafe (see safe_hardlink_source() above)
> * - not CAP_FOWNER in a namespace with the inode owner uid mapped
> *
> * Returns 0 if successful, -ve on error.
> */
> static int may_linkat(struct path *link)
> {
> struct inode *inode;
>
> 989 if (!sysctl_protected_hardlinks)
> return 0;
>
> 992 inode = link->dentry->d_inode;
>
> /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
> * otherwise, it must be a safe source.
> */
> 997 if (safe_hardlink_source(inode) || inode_owner_or_capable(inode))
> return 0;
>
> 1000 audit_log_link_denied("linkat");
> 1001 return -EPERM;
> }
>
> static __always_inline
> const char *get_link(struct nameidata *nd)
> {
> 1007 struct saved *last = nd->stack + nd->depth - 1;
> 1008 struct dentry *dentry = last->link.dentry;
> 1009 struct inode *inode = nd->link_inode;
> int error;
> const char *res;
>
> 1013 if (!(nd->flags & LOOKUP_RCU)) {
> 1014 touch_atime(&last->link);
> 1015 cond_resched();
> 1016 } else if (atime_needs_update_rcu(&last->link, inode)) {
> 1017 if (unlikely(unlazy_walk(nd)))
> 1018 return ERR_PTR(-ECHILD);
> 1019 touch_atime(&last->link);
> }
>
> 1022 error = security_inode_follow_link(dentry, inode,
> nd->flags & LOOKUP_RCU);
> 1024 if (unlikely(error))
> 1025 return ERR_PTR(error);
>
> 1027 nd->last_type = LAST_BIND;
> 1028 res = inode->i_link;
> 1029 if (!res) {
> const char * (*get)(struct dentry *, struct inode *,
> struct delayed_call *);
> 1032 get = inode->i_op->get_link;
> 1033 if (nd->flags & LOOKUP_RCU) {
> 1034 res = get(NULL, inode, &last->done);
> 1035 if (res == ERR_PTR(-ECHILD)) {
> 1036 if (unlikely(unlazy_walk(nd)))
> return ERR_PTR(-ECHILD);
> 1038 res = get(dentry, inode, &last->done);
> }
> } else {
> 1041 res = get(dentry, inode, &last->done);
> }
> if (IS_ERR_OR_NULL(res))
> return res;
> }
> 1046 if (*res == '/') {
> 1047 if (!nd->root.mnt)
> 1048 set_root(nd);
> 1049 if (unlikely(nd_jump_root(nd)))
> return ERR_PTR(-ECHILD);
> 1051 while (unlikely(*++res == '/'))
> ;
> }
> 1054 if (!*res)
> res = NULL;
> return res;
> }
>
> /*
> * follow_up - Find the mountpoint of path's vfsmount
> *
> * Given a path, find the mountpoint of its source file system.
> * Replace @path with the path of the mountpoint in the parent mount.
> * Up is towards /.
> *
> * Return 1 if we went up a level and 0 if we were already at the
> * root.
> */
> int follow_up(struct path *path)
> 1070 {
> 1071 struct mount *mnt = real_mount(path->mnt);
> struct mount *parent;
> struct dentry *mountpoint;
>
> read_seqlock_excl(&mount_lock);
> 1076 parent = mnt->mnt_parent;
> 1077 if (parent == mnt) {
> read_sequnlock_excl(&mount_lock);
> 1079 return 0;
> }
> 1081 mntget(&parent->mnt);
> 1082 mountpoint = dget(mnt->mnt_mountpoint);
> read_sequnlock_excl(&mount_lock);
> 1084 dput(path->dentry);
> 1085 path->dentry = mountpoint;
> 1086 mntput(path->mnt);
> 1087 path->mnt = &parent->mnt;
> 1088 return 1;
> 1089 }
> EXPORT_SYMBOL(follow_up);
>
> /*
> * Perform an automount
> * - return -EISDIR to tell follow_managed() to stop and return the path we
> * were called with.
> */
> static int follow_automount(struct path *path, struct nameidata *nd,
> bool *need_mntput)
> {
> struct vfsmount *mnt;
> int err;
>
> 1103 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
> return -EREMOTE;
>
> /* We don't want to mount if someone's just doing a stat -
> * unless they're stat'ing a directory and appended a '/' to
> * the name.
> *
> * We do, however, want to mount if someone wants to open or
> * create a file of any type under the mountpoint, wants to
> * traverse through the mountpoint or wants to open the
> * mounted directory. Also, autofs may mark negative dentries
> * as being automount points. These will need the attentions
> * of the daemon to instantiate them before they can be used.
> */
> 1117 if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
> 1118 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
> path->dentry->d_inode)
> 1120 return -EISDIR;
>
> 1122 nd->total_link_count++;
> 1123 if (nd->total_link_count >= 40)
> 1124 return -ELOOP;
>
> 1126 mnt = path->dentry->d_op->d_automount(path);
> 1127 if (IS_ERR(mnt)) {
> /*
> * The filesystem is allowed to return -EISDIR here to indicate
> * it doesn't want to automount. For instance, autofs would do
> * this so that its userspace daemon can mount on this dentry.
> *
> * However, we can only permit this if it's a terminal point in
> * the path being looked up; if it wasn't then the remainder of
> * the path is inaccessible and we should say so.
> */
> 1137 if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT))
> 1138 return -EREMOTE;
> 1139 return PTR_ERR(mnt);
> }
>
> 1142 if (!mnt) /* mount collision */
> 1143 return 0;
>
> 1145 if (!*need_mntput) {
> /* lock_mount() may release path->mnt on error */
> 1147 mntget(path->mnt);
> *need_mntput = true;
> }
> 1150 err = finish_automount(mnt, path);
>
> 1152 switch (err) {
> case -EBUSY:
> /* Someone else made a mount here whilst we were busy */
> 1155 return 0;
> case 0:
> path_put(path);
> 1158 path->mnt = mnt;
> 1159 path->dentry = dget(mnt->mnt_root);
> return 0;
> default:
> return err;
> }
>
> }
>
> /*
> * Handle a dentry that is managed in some way.
> * - Flagged for transit management (autofs)
> * - Flagged as mountpoint
> * - Flagged as automount point
> *
> * This may only be called in refwalk mode.
> *
> * Serialization is taken care of in namespace.c
> */
> static int follow_managed(struct path *path, struct nameidata *nd)
> 1178 {
> 1179 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
> unsigned managed;
> 1181 bool need_mntput = false;
> 1182 int ret = 0;
>
> /* Given that we're not holding a lock here, we retain the value in a
> * local variable for each dentry as we look at it so that we don't see
> * the components of that value change under us */
> 1187 while (managed = READ_ONCE(path->dentry->d_flags),
> managed &= DCACHE_MANAGED_DENTRY,
> unlikely(managed != 0)) {
> /* Allow the filesystem to manage the transit without i_mutex
> * being held. */
> 1192 if (managed & DCACHE_MANAGE_TRANSIT) {
> 1193 BUG_ON(!path->dentry->d_op);
> 1194 BUG_ON(!path->dentry->d_op->d_manage);
> 1195 ret = path->dentry->d_op->d_manage(path, false);
> 1196 if (ret < 0)
> break;
> }
>
> /* Transit to a mounted filesystem. */
> 1201 if (managed & DCACHE_MOUNTED) {
> 1202 struct vfsmount *mounted = lookup_mnt(path);
> 1203 if (mounted) {
> 1204 dput(path->dentry);
> 1205 if (need_mntput)
> 1206 mntput(path->mnt);
> 1207 path->mnt = mounted;
> 1208 path->dentry = dget(mounted->mnt_root);
> need_mntput = true;
> continue;
> }
>
> /* Something is mounted on this dentry in another
> * namespace and/or whatever was mounted there in this
> * namespace got unmounted before lookup_mnt() could
> * get it */
> }
>
> /* Handle an automount point */
> 1220 if (managed & DCACHE_NEED_AUTOMOUNT) {
> ret = follow_automount(path, nd, &need_mntput);
> 1222 if (ret < 0)
> break;
> continue;
> }
>
> /* We didn't change the current path point */
> break;
> }
>
> 1231 if (need_mntput && path->mnt == mnt)
> 1232 mntput(path->mnt);
> 1233 if (ret == -EISDIR || !ret)
> 1234 ret = 1;
> if (need_mntput)
> 1236 nd->flags |= LOOKUP_JUMPED;
> 1237 if (unlikely(ret < 0))
> path_put_conditional(path, nd);
> return ret;
> 1240 }
>
> int follow_down_one(struct path *path)
> 1243 {
> struct vfsmount *mounted;
>
> 1246 mounted = lookup_mnt(path);
> 1247 if (mounted) {
> 1248 dput(path->dentry);
> 1249 mntput(path->mnt);
> 1250 path->mnt = mounted;
> 1251 path->dentry = dget(mounted->mnt_root);
> 1252 return 1;
> }
> return 0;
> 1255 }
> EXPORT_SYMBOL(follow_down_one);
>
> static inline int managed_dentry_rcu(const struct path *path)
> {
> 1260 return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
> 1261 path->dentry->d_op->d_manage(path, true) : 0;
> }
>
> /*
> * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
> * we meet a managed dentry that would need blocking.
> */
> 1268 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
> struct inode **inode, unsigned *seqp)
> {
> for (;;) {
> struct mount *mounted;
> /*
> * Don't forget we might have a non-mountpoint managed dentry
> * that wants to block transit.
> */
> 1277 switch (managed_dentry_rcu(path)) {
> case -ECHILD:
> default:
> return false;
> case -EISDIR:
> 1282 return true;
> case 0:
> break;
> }
>
> 1287 if (!d_mountpoint(path->dentry))
> return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
>
> 1290 mounted = __lookup_mnt(path->mnt, path->dentry);
> 1291 if (!mounted)
> break;
> 1293 path->mnt = &mounted->mnt;
> 1294 path->dentry = mounted->mnt.mnt_root;
> 1295 nd->flags |= LOOKUP_JUMPED;
> 1296 *seqp = read_seqcount_begin(&path->dentry->d_seq);
> /*
> * Update the inode too. We don't need to re-check the
> * dentry sequence number here after this d_inode read,
> * because a mount-point is always pinned.
> */
> 1302 *inode = path->dentry->d_inode;
> }
> 1304 return !read_seqretry(&mount_lock, nd->m_seq) &&
> 1305 !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
> 1306 }
>
> static int follow_dotdot_rcu(struct nameidata *nd)
> {
> 1310 struct inode *inode = nd->inode;
>
> while (1) {
> if (path_equal(&nd->path, &nd->root))
> break;
> 1315 if (nd->path.dentry != nd->path.mnt->mnt_root) {
> struct dentry *old = nd->path.dentry;
> 1317 struct dentry *parent = old->d_parent;
> unsigned seq;
>
> 1320 inode = parent->d_inode;
> seq = read_seqcount_begin(&parent->d_seq);
> 1322 if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
> 1323 return -ECHILD;
> 1324 nd->path.dentry = parent;
> 1325 nd->seq = seq;
> 1326 if (unlikely(!path_connected(&nd->path)))
> 1327 return -ENOENT;
> break;
> } else {
> struct mount *mnt = real_mount(nd->path.mnt);
> 1331 struct mount *mparent = mnt->mnt_parent;
> 1332 struct dentry *mountpoint = mnt->mnt_mountpoint;
> 1333 struct inode *inode2 = mountpoint->d_inode;
> unsigned seq = read_seqcount_begin(&mountpoint->d_seq);
> 1335 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
> return -ECHILD;
> 1337 if (&mparent->mnt == nd->path.mnt)
> break;
> /* we know that mountpoint was pinned */
> 1340 nd->path.dentry = mountpoint;
> 1341 nd->path.mnt = &mparent->mnt;
> 1342 inode = inode2;
> 1343 nd->seq = seq;
> }
> }
> 1346 while (unlikely(d_mountpoint(nd->path.dentry))) {
> struct mount *mounted;
> 1348 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
> 1349 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
> return -ECHILD;
> 1351 if (!mounted)
> break;
> 1353 nd->path.mnt = &mounted->mnt;
> 1354 nd->path.dentry = mounted->mnt.mnt_root;
> 1355 inode = nd->path.dentry->d_inode;
> 1356 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
> }
> 1358 nd->inode = inode;
> 1359 return 0;
> }
>
> /*
> * Follow down to the covering mount currently visible to userspace. At each
> * point, the filesystem owning that dentry may be queried as to whether the
> * caller is permitted to proceed or not.
> */
> int follow_down(struct path *path)
> 1368 {
> unsigned managed;
> int ret;
>
> 1372 while (managed = READ_ONCE(path->dentry->d_flags),
> unlikely(managed & DCACHE_MANAGED_DENTRY)) {
> /* Allow the filesystem to manage the transit without i_mutex
> * being held.
> *
> * We indicate to the filesystem if someone is trying to mount
> * something here. This gives autofs the chance to deny anyone
> * other than its daemon the right to mount on its
> * superstructure.
> *
> * The filesystem may sleep at this point.
> */
> 1384 if (managed & DCACHE_MANAGE_TRANSIT) {
> 1385 BUG_ON(!path->dentry->d_op);
> 1386 BUG_ON(!path->dentry->d_op->d_manage);
> 1387 ret = path->dentry->d_op->d_manage(path, false);
> 1388 if (ret < 0)
> 1389 return ret == -EISDIR ? 0 : ret;
> }
>
> /* Transit to a mounted filesystem. */
> 1393 if (managed & DCACHE_MOUNTED) {
> 1394 struct vfsmount *mounted = lookup_mnt(path);
> 1395 if (!mounted)
> break;
> 1397 dput(path->dentry);
> 1398 mntput(path->mnt);
> 1399 path->mnt = mounted;
> 1400 path->dentry = dget(mounted->mnt_root);
> continue;
> }
>
> /* Don't handle automount points here */
> break;
> }
> 1407 return 0;
> 1408 }
> EXPORT_SYMBOL(follow_down);
>
> /*
> * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
> */
> static void follow_mount(struct path *path)
> 1415 {
> 1416 while (d_mountpoint(path->dentry)) {
> 1417 struct vfsmount *mounted = lookup_mnt(path);
> 1418 if (!mounted)
> break;
> 1420 dput(path->dentry);
> 1421 mntput(path->mnt);
> 1422 path->mnt = mounted;
> 1423 path->dentry = dget(mounted->mnt_root);
> }
> 1425 }
>
> static int path_parent_directory(struct path *path)
> 1428 {
> 1429 struct dentry *old = path->dentry;
> /* rare case of legitimate dget_parent()... */
> 1431 path->dentry = dget_parent(path->dentry);
> 1432 dput(old);
> 1433 if (unlikely(!path_connected(path)))
> return -ENOENT;
> 1435 return 0;
> 1436 }
>
> static int follow_dotdot(struct nameidata *nd)
> {
> while(1) {
> 1441 if (nd->path.dentry == nd->root.dentry &&
> nd->path.mnt == nd->root.mnt) {
> break;
> }
> 1445 if (nd->path.dentry != nd->path.mnt->mnt_root) {
> 1446 int ret = path_parent_directory(&nd->path);
> 1447 if (ret)
> return ret;
> break;
> }
> 1451 if (!follow_up(&nd->path))
> break;
> }
> 1454 follow_mount(&nd->path);
> 1455 nd->inode = nd->path.dentry->d_inode;
> 1456 return 0;
> }
>
> /*
> * This looks up the name in dcache and possibly revalidates the found dentry.
> * NULL is returned if the dentry does not exist in the cache.
> */
> static struct dentry *lookup_dcache(const struct qstr *name,
> struct dentry *dir,
> unsigned int flags)
> 1466 {
> 1467 struct dentry *dentry = d_lookup(dir, name);
> 1468 if (dentry) {
> int error = d_revalidate(dentry, flags);
> 1470 if (unlikely(error <= 0)) {
> 1471 if (!error)
> 1472 d_invalidate(dentry);
> 1473 dput(dentry);
> 1474 return ERR_PTR(error);
> }
> }
> return dentry;
> 1478 }
>
> /*
> * Parent directory has inode locked exclusive. This is one
> * and only case when ->lookup() gets called on non in-lookup
> * dentries - as the matter of fact, this only gets called
> * when directory is guaranteed to have no in-lookup children
> * at all.
> */
> static struct dentry *__lookup_hash(const struct qstr *name,
> struct dentry *base, unsigned int flags)
> 1489 {
> 1490 struct dentry *dentry = lookup_dcache(name, base, flags);
> struct dentry *old;
> 1492 struct inode *dir = base->d_inode;
>
> 1494 if (dentry)
> return dentry;
>
> /* Don't create child dentry for a dead directory. */
> 1498 if (unlikely(IS_DEADDIR(dir)))
> 1499 return ERR_PTR(-ENOENT);
>
> 1501 dentry = d_alloc(base, name);
> 1502 if (unlikely(!dentry))
> 1503 return ERR_PTR(-ENOMEM);
>
> 1505 old = dir->i_op->lookup(dir, dentry, flags);
> 1506 if (unlikely(old)) {
> 1507 dput(dentry);
> dentry = old;
> }
> return dentry;
> 1511 }
>
> static int lookup_fast(struct nameidata *nd,
> struct path *path, struct inode **inode,
> unsigned *seqp)
> 1516 {
> 1517 struct vfsmount *mnt = nd->path.mnt;
> 1518 struct dentry *dentry, *parent = nd->path.dentry;
> int status = 1;
> int err;
>
> /*
> * Rename seqlock is not required here because in the off chance
> * of a false negative due to a concurrent rename, the caller is
> * going to fall back to non-racy lookup.
> */
> 1527 if (nd->flags & LOOKUP_RCU) {
> unsigned seq;
> bool negative;
> 1530 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
> 1531 if (unlikely(!dentry)) {
> 1532 if (unlazy_walk(nd))
> 1533 return -ECHILD;
> return 0;
> }
>
> /*
> * This sequence count validates that the inode matches
> * the dentry name information from lookup.
> */
> 1541 *inode = d_backing_inode(dentry);
> negative = d_is_negative(dentry);
> 1543 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
> return -ECHILD;
>
> /*
> * This sequence count validates that the parent had no
> * changes while we did the lookup of the dentry above.
> *
> * The memory barrier in read_seqcount_begin of child is
> * enough, we can use __read_seqcount_retry here.
> */
> 1553 if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq)))
> return -ECHILD;
>
> 1556 *seqp = seq;
> status = d_revalidate(dentry, nd->flags);
> 1558 if (likely(status > 0)) {
> /*
> * Note: do negative dentry check after revalidation in
> * case that drops it.
> */
> 1563 if (unlikely(negative))
> return -ENOENT;
> 1565 path->mnt = mnt;
> 1566 path->dentry = dentry;
> 1567 if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
> 1568 return 1;
> }
> 1570 if (unlazy_child(nd, dentry, seq))
> 1571 return -ECHILD;
> 1572 if (unlikely(status == -ECHILD))
> /* we'd been told to redo it in non-rcu mode */
> status = d_revalidate(dentry, nd->flags);
> } else {
> 1576 dentry = __d_lookup(parent, &nd->last);
> 1577 if (unlikely(!dentry))
> 1578 return 0;
> status = d_revalidate(dentry, nd->flags);
> }
> 1581 if (unlikely(status <= 0)) {
> 1582 if (!status)
> 1583 d_invalidate(dentry);
> 1584 dput(dentry);
> 1585 return status;
> }
> 1587 if (unlikely(d_is_negative(dentry))) {
> 1588 dput(dentry);
> 1589 return -ENOENT;
> }
>
> 1592 path->mnt = mnt;
> 1593 path->dentry = dentry;
> 1594 err = follow_managed(path, nd);
> 1595 if (likely(err > 0))
> 1596 *inode = d_backing_inode(path->dentry);
> return err;
> 1598 }
>
> /* Fast lookup failed, do it the slow way */
> static struct dentry *__lookup_slow(const struct qstr *name,
> struct dentry *dir,
> unsigned int flags)
> 1604 {
> struct dentry *dentry, *old;
> 1606 struct inode *inode = dir->d_inode;
> 1607 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
>
> /* Don't go there if it's already dead */
> 1610 if (unlikely(IS_DEADDIR(inode)))
> 1611 return ERR_PTR(-ENOENT);
> again:
> 1613 dentry = d_alloc_parallel(dir, name, &wq);
> 1614 if (IS_ERR(dentry))
> return dentry;
> 1616 if (unlikely(!d_in_lookup(dentry))) {
> 1617 if (!(flags & LOOKUP_NO_REVAL)) {
> int error = d_revalidate(dentry, flags);
> 1619 if (unlikely(error <= 0)) {
> 1620 if (!error) {
> 1621 d_invalidate(dentry);
> 1622 dput(dentry);
> 1623 goto again;
> }
> 1625 dput(dentry);
> 1626 dentry = ERR_PTR(error);
> }
> }
> } else {
> 1630 old = inode->i_op->lookup(inode, dentry, flags);
> d_lookup_done(dentry);
> 1632 if (unlikely(old)) {
> 1633 dput(dentry);
> dentry = old;
> }
> }
> return dentry;
> 1638 }
>
> static struct dentry *lookup_slow(const struct qstr *name,
> struct dentry *dir,
> unsigned int flags)
> 1643 {
> struct inode *inode = dir->d_inode;
> struct dentry *res;
> inode_lock_shared(inode);
> 1647 res = __lookup_slow(name, dir, flags);
> inode_unlock_shared(inode);
> return res;
> 1650 }
>
> static inline int may_lookup(struct nameidata *nd)
> {
> 1654 if (nd->flags & LOOKUP_RCU) {
> 1655 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
> 1656 if (err != -ECHILD)
> return err;
> 1658 if (unlazy_walk(nd))
> return -ECHILD;
> }
> 1661 return inode_permission(nd->inode, MAY_EXEC);
> }
>
> static inline int handle_dots(struct nameidata *nd, int type)
> {
> 1666 if (type == LAST_DOTDOT) {
> 1667 if (!nd->root.mnt)
> 1668 set_root(nd);
> 1669 if (nd->flags & LOOKUP_RCU) {
> return follow_dotdot_rcu(nd);
> } else
> return follow_dotdot(nd);
> }
> 1674 return 0;
> }
>
> static int pick_link(struct nameidata *nd, struct path *link,
> struct inode *inode, unsigned seq)
> 1679 {
> int error;
> struct saved *last;
> 1682 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) {
> path_to_nameidata(link, nd);
> 1684 return -ELOOP;
> }
> 1686 if (!(nd->flags & LOOKUP_RCU)) {
> 1687 if (link->mnt == nd->path.mnt)
> 1688 mntget(link->mnt);
> }
> error = nd_alloc_stack(nd);
> 1691 if (unlikely(error)) {
> 1692 if (error == -ECHILD) {
> 1693 if (unlikely(!legitimize_path(nd, link, seq))) {
> drop_links(nd);
> 1695 nd->depth = 0;
> 1696 nd->flags &= ~LOOKUP_RCU;
> 1697 nd->path.mnt = NULL;
> 1698 nd->path.dentry = NULL;
> 1699 if (!(nd->flags & LOOKUP_ROOT))
> 1700 nd->root.mnt = NULL;
> rcu_read_unlock();
> 1702 } else if (likely(unlazy_walk(nd)) == 0)
> error = nd_alloc_stack(nd);
> }
> 1705 if (error) {
> path_put(link);
> 1707 return error;
> }
> }
>
> 1711 last = nd->stack + nd->depth++;
> 1712 last->link = *link;
> clear_delayed_call(&last->done);
> 1714 nd->link_inode = inode;
> 1715 last->seq = seq;
> 1716 return 1;
> 1717 }
>
> enum {WALK_FOLLOW = 1, WALK_MORE = 2};
>
> /*
> * Do we need to follow links? We _really_ want to be able
> * to do this check without having to look at inode->i_op,
> * so we keep a cache of "no, this doesn't need follow_link"
> * for the common case.
> */
> static inline int step_into(struct nameidata *nd, struct path *path,
> int flags, struct inode *inode, unsigned seq)
> {
> 1730 if (!(flags & WALK_MORE) && nd->depth)
> put_link(nd);
> 1732 if (likely(!d_is_symlink(path->dentry)) ||
> 1733 !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW)) {
> /* not a symlink or should not follow */
> path_to_nameidata(path, nd);
> 1736 nd->inode = inode;
> 1737 nd->seq = seq;
> return 0;
> }
> /* make sure that d_is_symlink above matches inode */
> 1741 if (nd->flags & LOOKUP_RCU) {
> 1742 if (read_seqcount_retry(&path->dentry->d_seq, seq))
> 1743 return -ECHILD;
> }
> 1745 return pick_link(nd, path, inode, seq);
> }
>
> static int walk_component(struct nameidata *nd, int flags)
> 1749 {
> struct path path;
> struct inode *inode;
> unsigned seq;
> int err;
> /*
> * "." and ".." are special - ".." especially so because it has
> * to be able to know about the current root directory and
> * parent relationships.
> */
> 1759 if (unlikely(nd->last_type != LAST_NORM)) {
> err = handle_dots(nd, nd->last_type);
> 1761 if (!(flags & WALK_MORE) && nd->depth)
> put_link(nd);
> return err;
> }
> 1765 err = lookup_fast(nd, &path, &inode, &seq);
> 1766 if (unlikely(err <= 0)) {
> 1767 if (err < 0)
> return err;
> 1769 path.dentry = lookup_slow(&nd->last, nd->path.dentry,
> nd->flags);
> 1771 if (IS_ERR(path.dentry))
> return PTR_ERR(path.dentry);
>
> 1774 path.mnt = nd->path.mnt;
> 1775 err = follow_managed(&path, nd);
> 1776 if (unlikely(err < 0))
> return err;
>
> 1779 if (unlikely(d_is_negative(path.dentry))) {
> path_to_nameidata(&path, nd);
> 1781 return -ENOENT;
> }
>
> 1784 seq = 0; /* we are already out of RCU mode */
> 1785 inode = d_backing_inode(path.dentry);
> }
>
> return step_into(nd, &path, flags, inode, seq);
> 1789 }
>
> /*
> * We can do the critical dentry name comparison and hashing
> * operations one word at a time, but we are limited to:
> *
> * - Architectures with fast unaligned word accesses. We could
> * do a "get_unaligned()" if this helps and is sufficiently
> * fast.
> *
> * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
> * do not trap on the (extremely unlikely) case of a page
> * crossing operation.
> *
> * - Furthermore, we need an efficient 64-bit compile for the
> * 64-bit case in order to generate the "number of bytes in
> * the final mask". Again, that could be replaced with a
> * efficient population count instruction or similar.
> */
> #ifdef CONFIG_DCACHE_WORD_ACCESS
>
> #include <asm/word-at-a-time.h>
>
> #ifdef HASH_MIX
>
> /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
>
> #elif defined(CONFIG_64BIT)
> /*
> * Register pressure in the mixing function is an issue, particularly
> * on 32-bit x86, but almost any function requires one state value and
> * one temporary. Instead, use a function designed for two state values
> * and no temporaries.
> *
> * This function cannot create a collision in only two iterations, so
> * we have two iterations to achieve avalanche. In those two iterations,
> * we have six layers of mixing, which is enough to spread one bit's
> * influence out to 2^6 = 64 state bits.
> *
> * Rotate constants are scored by considering either 64 one-bit input
> * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
> * probability of that delta causing a change to each of the 128 output
> * bits, using a sample of random initial states.
> *
> * The Shannon entropy of the computed probabilities is then summed
> * to produce a score. Ideally, any input change has a 50% chance of
> * toggling any given output bit.
> *
> * Mixing scores (in bits) for (12,45):
> * Input delta: 1-bit 2-bit
> * 1 round: 713.3 42542.6
> * 2 rounds: 2753.7 140389.8
> * 3 rounds: 5954.1 233458.2
> * 4 rounds: 7862.6 256672.2
> * Perfect: 8192 258048
> * (64*128) (64*63/2 * 128)
> */
> #define HASH_MIX(x, y, a) \
> ( x ^= (a), \
> y ^= x, x = rol64(x,12),\
> x += y, y = rol64(y,45),\
> y *= 9 )
>
> /*
> * Fold two longs into one 32-bit hash value. This must be fast, but
> * latency isn't quite as critical, as there is a fair bit of additional
> * work done before the hash value is used.
> */
> static inline unsigned int fold_hash(unsigned long x, unsigned long y)
> {
> 1859 y ^= x * GOLDEN_RATIO_64;
> 1860 y *= GOLDEN_RATIO_64;
> 1861 return y >> 32;
> }
>
> #else /* 32-bit case */
>
> /*
> * Mixing scores (in bits) for (7,20):
> * Input delta: 1-bit 2-bit
> * 1 round: 330.3 9201.6
> * 2 rounds: 1246.4 25475.4
> * 3 rounds: 1907.1 31295.1
> * 4 rounds: 2042.3 31718.6
> * Perfect: 2048 31744
> * (32*64) (32*31/2 * 64)
> */
> #define HASH_MIX(x, y, a) \
> ( x ^= (a), \
> y ^= x, x = rol32(x, 7),\
> x += y, y = rol32(y,20),\
> y *= 9 )
>
> static inline unsigned int fold_hash(unsigned long x, unsigned long y)
> {
> /* Use arch-optimized multiply if one exists */
> return __hash_32(y ^ __hash_32(x));
> }
>
> #endif
>
> /*
> * Return the hash of a string of known length. This is carfully
> * designed to match hash_name(), which is the more critical function.
> * In particular, we must end by hashing a final word containing 0..7
> * payload bytes, to match the way that hash_name() iterates until it
> * finds the delimiter after the name.
> */
> unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
> 1898 {
> 1899 unsigned long a, x = 0, y = (unsigned long)salt;
>
> for (;;) {
> 1902 if (!len)
> goto done;
> a = load_unaligned_zeropad(name);
> 1905 if (len < sizeof(unsigned long))
> break;
> 1907 HASH_MIX(x, y, a);
> 1908 name += sizeof(unsigned long);
> len -= sizeof(unsigned long);
> }
> 1911 x ^= a & bytemask_from_count(len);
> done:
> return fold_hash(x, y);
> 1914 }
> EXPORT_SYMBOL(full_name_hash);
>
> /* Return the "hash_len" (hash and length) of a null-terminated string */
> u64 hashlen_string(const void *salt, const char *name)
> 1919 {
> 1920 unsigned long a = 0, x = 0, y = (unsigned long)salt;
> unsigned long adata, mask, len;
> const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
>
> 1924 len = 0;
> 1925 goto inside;
>
> do {
> 1928 HASH_MIX(x, y, a);
> 1929 len += sizeof(unsigned long);
> inside:
> a = load_unaligned_zeropad(name+len);
> 1932 } while (!has_zero(a, &adata, &constants));
>
> adata = prep_zero_mask(a, adata, &constants);
> mask = create_zero_mask(adata);
> 1936 x ^= a & zero_bytemask(mask);
>
> 1938 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
> 1939 }
> EXPORT_SYMBOL(hashlen_string);
>
> /*
> * Calculate the length and hash of the path component, and
> * return the "hash_len" as the result.
> */
> static inline u64 hash_name(const void *salt, const char *name)
> {
> 1948 unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
> unsigned long adata, bdata, mask, len;
> const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
>
> 1952 len = 0;
> goto inside;
>
> do {
> 1956 HASH_MIX(x, y, a);
> 1957 len += sizeof(unsigned long);
> inside:
> a = load_unaligned_zeropad(name+len);
> 1960 b = a ^ REPEAT_BYTE('/');
> 1961 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
>
> adata = prep_zero_mask(a, adata, &constants);
> bdata = prep_zero_mask(b, bdata, &constants);
> mask = create_zero_mask(adata | bdata);
> 1966 x ^= a & zero_bytemask(mask);
>
> 1968 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
> }
>
> #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
>
> /* Return the hash of a string of known length */
> unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
> {
> unsigned long hash = init_name_hash(salt);
> while (len--)
> hash = partial_name_hash((unsigned char)*name++, hash);
> return end_name_hash(hash);
> }
> EXPORT_SYMBOL(full_name_hash);
>
> /* Return the "hash_len" (hash and length) of a null-terminated string */
> u64 hashlen_string(const void *salt, const char *name)
> {
> unsigned long hash = init_name_hash(salt);
> unsigned long len = 0, c;
>
> c = (unsigned char)*name;
> while (c) {
> len++;
> hash = partial_name_hash(c, hash);
> c = (unsigned char)name[len];
> }
> return hashlen_create(end_name_hash(hash), len);
> }
> EXPORT_SYMBOL(hashlen_string);
>
> /*
> * We know there's a real path component here of at least
> * one character.
> */
> static inline u64 hash_name(const void *salt, const char *name)
> {
> unsigned long hash = init_name_hash(salt);
> unsigned long len = 0, c;
>
> c = (unsigned char)*name;
> do {
> len++;
> hash = partial_name_hash(c, hash);
> c = (unsigned char)name[len];
> } while (c && c != '/');
> return hashlen_create(end_name_hash(hash), len);
> }
>
> #endif
>
> /*
> * Name resolution.
> * This is the basic name resolution function, turning a pathname into
> * the final dentry. We expect 'base' to be positive and a directory.
> *
> * Returns 0 and nd will have valid dentry and mnt on success.
> * Returns error and drops reference to input namei data on failure.
> */
> static int link_path_walk(const char *name, struct nameidata *nd)
> 2028 {
> int err;
>
> 2031 while (*name=='/')
> 2032 name++;
> 2033 if (!*name)
> 2034 return 0;
>
> /* At this point we know we have a real path component. */
> for(;;) {
> u64 hash_len;
> int type;
>
> err = may_lookup(nd);
> 2042 if (err)
> return err;
>
> 2045 hash_len = hash_name(nd->path.dentry, name);
>
> type = LAST_NORM;
> 2048 if (name[0] == '.') switch (hashlen_len(hash_len)) {
> case 2:
> 2050 if (name[1] == '.') {
> 2051 type = LAST_DOTDOT;
> 2052 nd->flags |= LOOKUP_JUMPED;
> }
> break;
> case 1:
> 2056 type = LAST_DOT;
> }
> if (likely(type == LAST_NORM)) {
> struct dentry *parent = nd->path.dentry;
> 2060 nd->flags &= ~LOOKUP_JUMPED;
> 2061 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
> 2062 struct qstr this = { { .hash_len = hash_len }, .name = name };
> 2063 err = parent->d_op->d_hash(parent, &this);
> 2064 if (err < 0)
> return err;
> 2066 hash_len = this.hash_len;
> 2067 name = this.name;
> }
> }
>
> 2071 nd->last.hash_len = hash_len;
> 2072 nd->last.name = name;
> 2073 nd->last_type = type;
>
> 2075 name += hashlen_len(hash_len);
> 2076 if (!*name)
> goto OK;
> /*
> * If it wasn't NUL, we know it was '/'. Skip that
> * slash, and continue until no more slashes.
> */
> do {
> 2083 name++;
> 2084 } while (unlikely(*name == '/'));
> 2085 if (unlikely(!*name)) {
> OK:
> /* pathname body, done */
> 2088 if (!nd->depth)
> return 0;
> 2090 name = nd->stack[nd->depth - 1].name;
> /* trailing symlink, done */
> 2092 if (!name)
> return 0;
> /* last component of nested symlink */
> 2095 err = walk_component(nd, WALK_FOLLOW);
> } else {
> /* not the last component */
> 2098 err = walk_component(nd, WALK_FOLLOW | WALK_MORE);
> }
> 2100 if (err < 0)
> return err;
>
> 2103 if (err) {
> const char *s = get_link(nd);
>
> 2106 if (IS_ERR(s))
> 2107 return PTR_ERR(s);
> err = 0;
> 2109 if (unlikely(!s)) {
> /* jumped */
> put_link(nd);
> } else {
> 2113 nd->stack[nd->depth - 1].name = name;
> name = s;
> 2115 continue;
> }
> }
> 2118 if (unlikely(!d_can_lookup(nd->path.dentry))) {
> 2119 if (nd->flags & LOOKUP_RCU) {
> 2120 if (unlazy_walk(nd))
> return -ECHILD;
> }
> 2123 return -ENOTDIR;
> }
> }
> 2126 }
>
> static const char *path_init(struct nameidata *nd, unsigned flags)
> 2129 {
> 2130 const char *s = nd->name->name;
>
> 2132 if (!*s)
> 2133 flags &= ~LOOKUP_RCU;
>
> 2135 nd->last_type = LAST_ROOT; /* if there are only slashes... */
> 2136 nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
> nd->depth = 0;
> 2138 if (flags & LOOKUP_ROOT) {
> 2139 struct dentry *root = nd->root.dentry;
> 2140 struct inode *inode = root->d_inode;
> 2141 if (*s && unlikely(!d_can_lookup(root)))
> return ERR_PTR(-ENOTDIR);
> 2143 nd->path = nd->root;
> 2144 nd->inode = inode;
> 2145 if (flags & LOOKUP_RCU) {
> rcu_read_lock();
> 2147 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
> 2148 nd->root_seq = nd->seq;
> 2149 nd->m_seq = read_seqbegin(&mount_lock);
> } else {
> 2151 path_get(&nd->path);
> }
> return s;
> }
>
> 2156 nd->root.mnt = NULL;
> 2157 nd->path.mnt = NULL;
> 2158 nd->path.dentry = NULL;
>
> 2160 nd->m_seq = read_seqbegin(&mount_lock);
> 2161 if (*s == '/') {
> if (flags & LOOKUP_RCU)
> rcu_read_lock();
> 2164 set_root(nd);
> 2165 if (likely(!nd_jump_root(nd)))
> return s;
> 2167 nd->root.mnt = NULL;
> rcu_read_unlock();
> 2169 return ERR_PTR(-ECHILD);
> 2170 } else if (nd->dfd == AT_FDCWD) {
> 2171 if (flags & LOOKUP_RCU) {
> 2172 struct fs_struct *fs = current->fs;
> unsigned seq;
>
> rcu_read_lock();
>
> do {
> seq = read_seqcount_begin(&fs->seq);
> 2179 nd->path = fs->pwd;
> 2180 nd->inode = nd->path.dentry->d_inode;
> 2181 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
> 2182 } while (read_seqcount_retry(&fs->seq, seq));
> } else {
> 2184 get_fs_pwd(current->fs, &nd->path);
> 2185 nd->inode = nd->path.dentry->d_inode;
> }
> return s;
> } else {
> /* Caller must check execute permissions on the starting path component */
> struct fd f = fdget_raw(nd->dfd);
> struct dentry *dentry;
>
> 2193 if (!f.file)
> 2194 return ERR_PTR(-EBADF);
>
> 2196 dentry = f.file->f_path.dentry;
>
> 2198 if (*s) {
> 2199 if (!d_can_lookup(dentry)) {
> fdput(f);
> 2201 return ERR_PTR(-ENOTDIR);
> }
> }
>
> 2205 nd->path = f.file->f_path;
> 2206 if (flags & LOOKUP_RCU) {
> rcu_read_lock();
> 2208 nd->inode = nd->path.dentry->d_inode;
> 2209 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
> } else {
> 2211 path_get(&nd->path);
> 2212 nd->inode = nd->path.dentry->d_inode;
> }
> fdput(f);
> return s;
> }
> 2217 }
>
> static const char *trailing_symlink(struct nameidata *nd)
> 2220 {
> const char *s;
> int error = may_follow_link(nd);
> if (unlikely(error))
> return ERR_PTR(error);
> 2225 nd->flags |= LOOKUP_PARENT;
> 2226 nd->stack[0].name = NULL;
> s = get_link(nd);
> 2228 return s ? s : "";
> 2229 }
>
> static inline int lookup_last(struct nameidata *nd)
> {
> 2233 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
> 2234 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
>
> 2236 nd->flags &= ~LOOKUP_PARENT;
> 2237 return walk_component(nd, 0);
> }
>
> static int handle_lookup_down(struct nameidata *nd)
> {
> 2242 struct path path = nd->path;
> 2243 struct inode *inode = nd->inode;
> 2244 unsigned seq = nd->seq;
> int err;
>
> 2247 if (nd->flags & LOOKUP_RCU) {
> /*
> * don't bother with unlazy_walk on failure - we are
> * at the very beginning of walk, so we lose nothing
> * if we simply redo everything in non-RCU mode
> */
> 2253 if (unlikely(!__follow_mount_rcu(nd, &path, &inode, &seq)))
> 2254 return -ECHILD;
> } else {
> 2256 dget(path.dentry);
> 2257 err = follow_managed(&path, nd);
> 2258 if (unlikely(err < 0))
> return err;
> 2260 inode = d_backing_inode(path.dentry);
> 2261 seq = 0;
> }
> path_to_nameidata(&path, nd);
> 2264 nd->inode = inode;
> 2265 nd->seq = seq;
> return 0;
> }
>
> /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
> static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
> 2271 {
> 2272 const char *s = path_init(nd, flags);
> int err;
>
> 2275 if (IS_ERR(s))
> return PTR_ERR(s);
>
> 2278 if (unlikely(flags & LOOKUP_DOWN)) {
> err = handle_lookup_down(nd);
> if (unlikely(err < 0)) {
> terminate_walk(nd);
> return err;
> }
> }
>
> 2286 while (!(err = link_path_walk(s, nd))
> 2287 && ((err = lookup_last(nd)) > 0)) {
> 2288 s = trailing_symlink(nd);
> 2289 if (IS_ERR(s)) {
> err = PTR_ERR(s);
> break;
> }
> }
> 2294 if (!err)
> 2295 err = complete_walk(nd);
>
> 2297 if (!err && nd->flags & LOOKUP_DIRECTORY)
> 2298 if (!d_can_lookup(nd->path.dentry))
> 2299 err = -ENOTDIR;
> if (!err) {
> 2301 *path = nd->path;
> 2302 nd->path.mnt = NULL;
> 2303 nd->path.dentry = NULL;
> }
> 2305 terminate_walk(nd);
> return err;
> 2307 }
>
> static int filename_lookup(int dfd, struct filename *name, unsigned flags,
> struct path *path, struct path *root)
> 2311 {
> int retval;
> struct nameidata nd;
> 2314 if (IS_ERR(name))
> 2315 return PTR_ERR(name);
> 2316 if (unlikely(root)) {
> 2317 nd.root = *root;
> 2318 flags |= LOOKUP_ROOT;
> }
> set_nameidata(&nd, dfd, name);
> 2321 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
> 2322 if (unlikely(retval == -ECHILD))
> 2323 retval = path_lookupat(&nd, flags, path);
> 2324 if (unlikely(retval == -ESTALE))
> 2325 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
>
> 2327 if (likely(!retval))
> audit_inode(name, path->dentry, flags & LOOKUP_PARENT);
> 2329 restore_nameidata();
> 2330 putname(name);
> return retval;
> 2332 }
>
> /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
> static int path_parentat(struct nameidata *nd, unsigned flags,
> struct path *parent)
> 2337 {
> 2338 const char *s = path_init(nd, flags);
> int err;
> 2340 if (IS_ERR(s))
> 2341 return PTR_ERR(s);
> 2342 err = link_path_walk(s, nd);
> 2343 if (!err)
> 2344 err = complete_walk(nd);
> 2345 if (!err) {
> 2346 *parent = nd->path;
> 2347 nd->path.mnt = NULL;
> 2348 nd->path.dentry = NULL;
> }
> 2350 terminate_walk(nd);
> return err;
> 2352 }
>
> static struct filename *filename_parentat(int dfd, struct filename *name,
> unsigned int flags, struct path *parent,
> struct qstr *last, int *type)
> 2357 {
> int retval;
> struct nameidata nd;
>
> 2361 if (IS_ERR(name))
> return name;
> set_nameidata(&nd, dfd, name);
> 2364 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
> 2365 if (unlikely(retval == -ECHILD))
> 2366 retval = path_parentat(&nd, flags, parent);
> 2367 if (unlikely(retval == -ESTALE))
> 2368 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
> 2369 if (likely(!retval)) {
> 2370 *last = nd.last;
> 2371 *type = nd.last_type;
> audit_inode(name, parent->dentry, LOOKUP_PARENT);
> } else {
> 2374 putname(name);
> 2375 name = ERR_PTR(retval);
> }
> 2377 restore_nameidata();
> return name;
> 2379 }
>
> /* does lookup, returns the object with parent locked */
> struct dentry *kern_path_locked(const char *name, struct path *path)
> 2383 {
> struct filename *filename;
> struct dentry *d;
> struct qstr last;
> int type;
>
> 2389 filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path,
> &last, &type);
> 2391 if (IS_ERR(filename))
> 2392 return ERR_CAST(filename);
> 2393 if (unlikely(type != LAST_NORM)) {
> path_put(path);
> 2395 putname(filename);
> 2396 return ERR_PTR(-EINVAL);
> }
> inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
> 2399 d = __lookup_hash(&last, path->dentry, 0);
> 2400 if (IS_ERR(d)) {
> 2401 inode_unlock(path->dentry->d_inode);
> path_put(path);
> }
> 2404 putname(filename);
> return d;
> 2406 }
>
> int kern_path(const char *name, unsigned int flags, struct path *path)
> 2409 {
> 2410 return filename_lookup(AT_FDCWD, getname_kernel(name),
> flags, path, NULL);
> 2412 }
> EXPORT_SYMBOL(kern_path);
>
> /**
> * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
> * @dentry: pointer to dentry of the base directory
> * @mnt: pointer to vfs mount of the base directory
> * @name: pointer to file name
> * @flags: lookup flags
> * @path: pointer to struct path to fill
> */
> int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
> const char *name, unsigned int flags,
> struct path *path)
> 2426 {
> 2427 struct path root = {.mnt = mnt, .dentry = dentry};
> /* the first argument of filename_lookup() is ignored with root */
> 2429 return filename_lookup(AT_FDCWD, getname_kernel(name),
> flags , path, &root);
> 2431 }
> EXPORT_SYMBOL(vfs_path_lookup);
>
> static int lookup_one_len_common(const char *name, struct dentry *base,
> int len, struct qstr *this)
> 2436 {
> 2437 this->name = name;
> 2438 this->len = len;
> 2439 this->hash = full_name_hash(base, name, len);
> 2440 if (!len)
> 2441 return -EACCES;
>
> 2443 if (unlikely(name[0] == '.')) {
> 2444 if (len < 2 || (len == 2 && name[1] == '.'))
> return -EACCES;
> }
>
> 2448 while (len--) {
> 2449 unsigned int c = *(const unsigned char *)name++;
> 2450 if (c == '/' || c == '\0')
> return -EACCES;
> }
> /*
> * See if the low-level filesystem might want
> * to use its own hash..
> */
> 2457 if (base->d_flags & DCACHE_OP_HASH) {
> 2458 int err = base->d_op->d_hash(base, this);
> 2459 if (err < 0)
> return err;
> }
>
> 2463 return inode_permission(base->d_inode, MAY_EXEC);
> 2464 }
>
> /**
> * lookup_one_len - filesystem helper to lookup single pathname component
> * @name: pathname component to lookup
> * @base: base directory to lookup from
> * @len: maximum length @len should be interpreted to
> *
> * Note that this routine is purely a helper for filesystem usage and should
> * not be called by generic code.
> *
> * The caller must hold base->i_mutex.
> */
> struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
> 2478 {
> struct dentry *dentry;
> struct qstr this;
> int err;
>
> 2483 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
>
> 2485 err = lookup_one_len_common(name, base, len, &this);
> 2486 if (err)
> 2487 return ERR_PTR(err);
>
> 2489 dentry = lookup_dcache(&this, base, 0);
> 2490 return dentry ? dentry : __lookup_slow(&this, base, 0);
> 2491 }
> EXPORT_SYMBOL(lookup_one_len);
>
> /**
> * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
> * @name: pathname component to lookup
> * @base: base directory to lookup from
> * @len: maximum length @len should be interpreted to
> *
> * Note that this routine is purely a helper for filesystem usage and should
> * not be called by generic code.
> *
> * Unlike lookup_one_len, it should be called without the parent
> * i_mutex held, and will take the i_mutex itself if necessary.
> */
> struct dentry *lookup_one_len_unlocked(const char *name,
> struct dentry *base, int len)
> 2508 {
> struct qstr this;
> int err;
> struct dentry *ret;
>
> 2513 err = lookup_one_len_common(name, base, len, &this);
> 2514 if (err)
> 2515 return ERR_PTR(err);
>
> 2517 ret = lookup_dcache(&this, base, 0);
> 2518 if (!ret)
> 2519 ret = lookup_slow(&this, base, 0);
> return ret;
> 2521 }
> EXPORT_SYMBOL(lookup_one_len_unlocked);
>
> #ifdef CONFIG_UNIX98_PTYS
> int path_pts(struct path *path)
> 2526 {
> /* Find something mounted on "pts" in the same directory as
> * the input path.
> */
> struct dentry *child, *parent;
> struct qstr this;
> int ret;
>
> 2534 ret = path_parent_directory(path);
> 2535 if (ret)
> return ret;
>
> 2538 parent = path->dentry;
> 2539 this.name = "pts";
> 2540 this.len = 3;
> 2541 child = d_hash_and_lookup(parent, &this);
> 2542 if (!child)
> 2543 return -ENOENT;
>
> 2545 path->dentry = child;
> 2546 dput(parent);
> 2547 follow_mount(path);
> 2548 return 0;
> 2549 }
> #endif
>
> int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
> struct path *path, int *empty)
> 2554 {
> 2555 return filename_lookup(dfd, getname_flags(name, flags, empty),
> flags, path, NULL);
> 2557 }
> EXPORT_SYMBOL(user_path_at_empty);
>
> /**
> * mountpoint_last - look up last component for umount
> * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
> *
> * This is a special lookup_last function just for umount. In this case, we
> * need to resolve the path without doing any revalidation.
> *
> * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
> * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
> * in almost all cases, this lookup will be served out of the dcache. The only
> * cases where it won't are if nd->last refers to a symlink or the path is
> * bogus and it doesn't exist.
> *
> * Returns:
> * -error: if there was an error during lookup. This includes -ENOENT if the
> * lookup found a negative dentry.
> *
> * 0: if we successfully resolved nd->last and found it to not to be a
> * symlink that needs to be followed.
> *
> * 1: if we successfully resolved nd->last and found it to be a symlink
> * that needs to be followed.
> */
> static int
> mountpoint_last(struct nameidata *nd)
> {
> int error = 0;
> 2587 struct dentry *dir = nd->path.dentry;
> struct path path;
>
> /* If we're in rcuwalk, drop out of it to handle last component */
> 2591 if (nd->flags & LOOKUP_RCU) {
> 2592 if (unlazy_walk(nd))
> return -ECHILD;
> }
>
> 2596 nd->flags &= ~LOOKUP_PARENT;
>
> 2598 if (unlikely(nd->last_type != LAST_NORM)) {
> error = handle_dots(nd, nd->last_type);
> if (error)
> return error;
> 2602 path.dentry = dget(nd->path.dentry);
> } else {
> 2604 path.dentry = d_lookup(dir, &nd->last);
> 2605 if (!path.dentry) {
> /*
> * No cached dentry. Mounted dentries are pinned in the
> * cache, so that means that this dentry is probably
> * a symlink or the path doesn't actually point
> * to a mounted dentry.
> */
> 2612 path.dentry = lookup_slow(&nd->last, dir,
> nd->flags | LOOKUP_NO_REVAL);
> 2614 if (IS_ERR(path.dentry))
> return PTR_ERR(path.dentry);
> }
> }
> 2618 if (d_is_negative(path.dentry)) {
> 2619 dput(path.dentry);
> 2620 return -ENOENT;
> }
> 2622 path.mnt = nd->path.mnt;
> 2623 return step_into(nd, &path, 0, d_backing_inode(path.dentry), 0);
> }
>
> /**
> * path_mountpoint - look up a path to be umounted
> * @nd: lookup context
> * @flags: lookup flags
> * @path: pointer to container for result
> *
> * Look up the given name, but don't attempt to revalidate the last component.
> * Returns 0 and "path" will be valid on success; Returns error otherwise.
> */
> static int
> path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path)
> 2637 {
> 2638 const char *s = path_init(nd, flags);
> int err;
> 2640 if (IS_ERR(s))
> 2641 return PTR_ERR(s);
> 2642 while (!(err = link_path_walk(s, nd)) &&
> (err = mountpoint_last(nd)) > 0) {
> 2644 s = trailing_symlink(nd);
> 2645 if (IS_ERR(s)) {
> err = PTR_ERR(s);
> break;
> }
> }
> 2650 if (!err) {
> 2651 *path = nd->path;
> 2652 nd->path.mnt = NULL;
> 2653 nd->path.dentry = NULL;
> 2654 follow_mount(path);
> }
> 2656 terminate_walk(nd);
> return err;
> 2658 }
>
> static int
> filename_mountpoint(int dfd, struct filename *name, struct path *path,
> unsigned int flags)
> 2663 {
> struct nameidata nd;
> int error;
> 2666 if (IS_ERR(name))
> 2667 return PTR_ERR(name);
> set_nameidata(&nd, dfd, name);
> 2669 error = path_mountpoint(&nd, flags | LOOKUP_RCU, path);
> 2670 if (unlikely(error == -ECHILD))
> 2671 error = path_mountpoint(&nd, flags, path);
> 2672 if (unlikely(error == -ESTALE))
> 2673 error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path);
> 2674 if (likely(!error))
> audit_inode(name, path->dentry, 0);
> 2676 restore_nameidata();
> 2677 putname(name);
> return error;
> 2679 }
>
> /**
> * user_path_mountpoint_at - lookup a path from userland in order to umount it
> * @dfd: directory file descriptor
> * @name: pathname from userland
> * @flags: lookup flags
> * @path: pointer to container to hold result
> *
> * A umount is a special case for path walking. We're not actually interested
> * in the inode in this situation, and ESTALE errors can be a problem. We
> * simply want track down the dentry and vfsmount attached at the mountpoint
> * and avoid revalidating the last component.
> *
> * Returns 0 and populates "path" on success.
> */
> int
> user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
> struct path *path)
> 2698 {
> 2699 return filename_mountpoint(dfd, getname(name), path, flags);
> 2700 }
>
> int
> kern_path_mountpoint(int dfd, const char *name, struct path *path,
> unsigned int flags)
> 2705 {
> 2706 return filename_mountpoint(dfd, getname_kernel(name), path, flags);
> 2707 }
> EXPORT_SYMBOL(kern_path_mountpoint);
>
> int __check_sticky(struct inode *dir, struct inode *inode)
> 2711 {
> 2712 kuid_t fsuid = current_fsuid();
>
> 2714 if (uid_eq(inode->i_uid, fsuid))
> 2715 return 0;
> 2716 if (uid_eq(dir->i_uid, fsuid))
> return 0;
> 2718 return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
> 2719 }
> EXPORT_SYMBOL(__check_sticky);
>
> /*
> * Check whether we can remove a link victim from directory dir, check
> * whether the type of victim is right.
> * 1. We can't do it if dir is read-only (done in permission())
> * 2. We should have write and exec permissions on dir
> * 3. We can't remove anything from append-only dir
> * 4. We can't do anything with immutable dir (done in permission())
> * 5. If the sticky bit on dir is set we should either
> * a. be owner of dir, or
> * b. be owner of victim, or
> * c. have CAP_FOWNER capability
> * 6. If the victim is append-only or immutable we can't do antyhing with
> * links pointing to it.
> * 7. If the victim has an unknown uid or gid we can't change the inode.
> * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
> * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
> * 10. We can't remove a root or mountpoint.
> * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
> * nfs_async_unlink().
> */
> static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
> 2743 {
> 2744 struct inode *inode = d_backing_inode(victim);
> int error;
>
> 2747 if (d_is_negative(victim))
> 2748 return -ENOENT;
> 2749 BUG_ON(!inode);
>
> 2751 BUG_ON(victim->d_parent->d_inode != dir);
> audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
>
> 2754 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
> 2755 if (error)
> return error;
> 2757 if (IS_APPEND(dir))
> 2758 return -EPERM;
>
> 2760 if (check_sticky(dir, inode) || IS_APPEND(inode) ||
> 2761 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode))
> return -EPERM;
> 2763 if (isdir) {
> if (!d_is_dir(victim))
> 2765 return -ENOTDIR;
> 2766 if (IS_ROOT(victim))
> return -EBUSY;
> } else if (d_is_dir(victim))
> 2769 return -EISDIR;
> 2770 if (IS_DEADDIR(dir))
> return -ENOENT;
> if (victim->d_flags & DCACHE_NFSFS_RENAMED)
> 2773 return -EBUSY;
> return 0;
> 2775 }
>
> /* Check whether we can create an object with dentry child in directory
> * dir.
> * 1. We can't do it if child already exists (open has special treatment for
> * this case, but since we are inlined it's OK)
> * 2. We can't do it if dir is read-only (done in permission())
> * 3. We can't do it if the fs can't represent the fsuid or fsgid.
> * 4. We should have write and exec permissions on dir
> * 5. We can't do it if dir is immutable (done in permission())
> */
> static inline int may_create(struct inode *dir, struct dentry *child)
> {
> struct user_namespace *s_user_ns;
> audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
> 2790 if (child->d_inode)
> 2791 return -EEXIST;
> 2792 if (IS_DEADDIR(dir))
> 2793 return -ENOENT;
> 2794 s_user_ns = dir->i_sb->s_user_ns;
> 2795 if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
> !kgid_has_mapping(s_user_ns, current_fsgid()))
> 2797 return -EOVERFLOW;
> 2798 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
> }
>
> /*
> * p1 and p2 should be directories on the same fs.
> */
> struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
> 2805 {
> struct dentry *p;
>
> 2808 if (p1 == p2) {
> inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
> 2810 return NULL;
> }
>
> 2813 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
>
> 2815 p = d_ancestor(p2, p1);
> 2816 if (p) {
> inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
> inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
> return p;
> }
>
> 2822 p = d_ancestor(p1, p2);
> if (p) {
> inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
> inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
> return p;
> }
>
> inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
> inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
> return NULL;
> 2832 }
> EXPORT_SYMBOL(lock_rename);
>
> void unlock_rename(struct dentry *p1, struct dentry *p2)
> 2836 {
> inode_unlock(p1->d_inode);
> 2838 if (p1 != p2) {
> inode_unlock(p2->d_inode);
> 2840 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
> }
> 2842 }
> EXPORT_SYMBOL(unlock_rename);
>
> int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
> bool want_excl)
> 2847 {
> int error = may_create(dir, dentry);
> 2849 if (error)
> return error;
>
> 2852 if (!dir->i_op->create)
> 2853 return -EACCES; /* shouldn't it be ENOSYS? */
> mode &= S_IALLUGO;
> 2855 mode |= S_IFREG;
> 2856 error = security_inode_create(dir, dentry, mode);
> 2857 if (error)
> return error;
> 2859 error = dir->i_op->create(dir, dentry, mode, want_excl);
> 2860 if (!error)
> fsnotify_create(dir, dentry);
> return error;
> 2863 }
> EXPORT_SYMBOL(vfs_create);
>
> int vfs_mkobj(struct dentry *dentry, umode_t mode,
> int (*f)(struct dentry *, umode_t, void *),
> void *arg)
> 2869 {
> 2870 struct inode *dir = dentry->d_parent->d_inode;
> int error = may_create(dir, dentry);
> 2872 if (error)
> return error;
>
> mode &= S_IALLUGO;
> 2876 mode |= S_IFREG;
> 2877 error = security_inode_create(dir, dentry, mode);
> 2878 if (error)
> return error;
> 2880 error = f(dentry, mode, arg);
> 2881 if (!error)
> fsnotify_create(dir, dentry);
> return error;
> 2884 }
> EXPORT_SYMBOL(vfs_mkobj);
>
> bool may_open_dev(const struct path *path)
> 2888 {
> 2889 return !(path->mnt->mnt_flags & MNT_NODEV) &&
> 2890 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
> 2891 }
>
> static int may_open(const struct path *path, int acc_mode, int flag)
> 2894 {
> struct dentry *dentry = path->dentry;
> 2896 struct inode *inode = dentry->d_inode;
> int error;
>
> 2899 if (!inode)
> 2900 return -ENOENT;
>
> 2902 switch (inode->i_mode & S_IFMT) {
> case S_IFLNK:
> 2904 return -ELOOP;
> case S_IFDIR:
> 2906 if (acc_mode & MAY_WRITE)
> 2907 return -EISDIR;
> break;
> case S_IFBLK:
> case S_IFCHR:
> if (!may_open_dev(path))
> 2912 return -EACCES;
> /*FALLTHRU*/
> case S_IFIFO:
> case S_IFSOCK:
> 2916 flag &= ~O_TRUNC;
> break;
> }
>
> 2920 error = inode_permission(inode, MAY_OPEN | acc_mode);
> 2921 if (error)
> return error;
>
> /*
> * An append-only file must be opened in append mode for writing.
> */
> 2927 if (IS_APPEND(inode)) {
> 2928 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
> 2929 return -EPERM;
> 2930 if (flag & O_TRUNC)
> return -EPERM;
> }
>
> /* O_NOATIME can only be set by the owner or superuser */
> 2935 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
> return -EPERM;
>
> return 0;
> 2939 }
>
> static int handle_truncate(struct file *filp)
> {
> const struct path *path = &filp->f_path;
> 2944 struct inode *inode = path->dentry->d_inode;
> int error = get_write_access(inode);
> if (error)
> return error;
> /*
> * Refuse to truncate files with mandatory locks held on them.
> */
> error = locks_verify_locked(filp);
> if (!error)
> error = security_path_truncate(path);
> if (!error) {
> 2955 error = do_truncate(path->dentry, 0,
> ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
> filp);
> }
> put_write_access(inode);
> return error;
> }
>
> static inline int open_to_namei_flags(int flag)
> {
> 2965 if ((flag & O_ACCMODE) == 3)
> 2966 flag--;
> return flag;
> }
>
> static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode)
> {
> struct user_namespace *s_user_ns;
> int error = security_path_mknod(dir, dentry, mode, 0);
> if (error)
> return error;
>
> 2977 s_user_ns = dir->dentry->d_sb->s_user_ns;
> 2978 if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
> !kgid_has_mapping(s_user_ns, current_fsgid()))
> 2980 return -EOVERFLOW;
>
> 2982 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
> 2983 if (error)
> return error;
>
> 2986 return security_inode_create(dir->dentry->d_inode, dentry, mode);
> }
>
> /*
> * Attempt to atomically look up, create and open a file from a negative
> * dentry.
> *
> * Returns 0 if successful. The file will have been created and attached to
> * @file by the filesystem calling finish_open().
> *
> * Returns 1 if the file was looked up only or didn't need creating. The
> * caller will need to perform the open themselves. @path will have been
> * updated to point to the new dentry. This may be negative.
> *
> * Returns an error code otherwise.
> */
> static int atomic_open(struct nameidata *nd, struct dentry *dentry,
> struct path *path, struct file *file,
> const struct open_flags *op,
> int open_flag, umode_t mode,
> int *opened)
> {
> struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
> 3009 struct inode *dir = nd->path.dentry->d_inode;
> int error;
>
> 3012 if (!(~open_flag & (O_EXCL | O_CREAT))) /* both O_EXCL and O_CREAT */
> 3013 open_flag &= ~O_TRUNC;
>
> if (nd->flags & LOOKUP_DIRECTORY)
> 3016 open_flag |= O_DIRECTORY;
>
> 3018 file->f_path.dentry = DENTRY_NOT_SET;
> 3019 file->f_path.mnt = nd->path.mnt;
> 3020 error = dir->i_op->atomic_open(dir, dentry, file,
> open_to_namei_flags(open_flag),
> mode, opened);
> d_lookup_done(dentry);
> 3024 if (!error) {
> /*
> * We didn't have the inode before the open, so check open
> * permission here.
> */
> 3029 int acc_mode = op->acc_mode;
> 3030 if (*opened & FILE_CREATED) {
> 3031 WARN_ON(!(open_flag & O_CREAT));
> fsnotify_create(dir, dentry);
> acc_mode = 0;
> }
> 3035 error = may_open(&file->f_path, acc_mode, open_flag);
> 3036 if (WARN_ON(error > 0))
> 3037 error = -EINVAL;
> 3038 } else if (error > 0) {
> 3039 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
> 3040 error = -EIO;
> } else {
> 3042 if (file->f_path.dentry) {
> 3043 dput(dentry);
> 3044 dentry = file->f_path.dentry;
> }
> 3046 if (*opened & FILE_CREATED)
> fsnotify_create(dir, dentry);
> 3048 if (unlikely(d_is_negative(dentry))) {
> error = -ENOENT;
> } else {
> path->dentry = dentry;
> path->mnt = nd->path.mnt;
> return 1;
> }
> }
> }
> 3057 dput(dentry);
> return error;
> }
>
> /*
> * Look up and maybe create and open the last component.
> *
> * Must be called with i_mutex held on parent.
> *
> * Returns 0 if the file was successfully atomically created (if necessary) and
> * opened. In this case the file will be returned attached to @file.
> *
> * Returns 1 if the file was not completely opened at this time, though lookups
> * and creations will have been performed and the dentry returned in @path will
> * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
> * specified then a negative dentry may be returned.
> *
> * An error code is returned otherwise.
> *
> * FILE_CREATE will be set in @*opened if the dentry was created and will be
> * cleared otherwise prior to returning.
> */
> static int lookup_open(struct nameidata *nd, struct path *path,
> struct file *file,
> const struct open_flags *op,
> bool got_write, int *opened)
> {
> 3084 struct dentry *dir = nd->path.dentry;
> 3085 struct inode *dir_inode = dir->d_inode;
> 3086 int open_flag = op->open_flag;
> struct dentry *dentry;
> int error, create_error = 0;
> 3089 umode_t mode = op->mode;
> 3090 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
>
> 3092 if (unlikely(IS_DEADDIR(dir_inode)))
> 3093 return -ENOENT;
>
> 3095 *opened &= ~FILE_CREATED;
> 3096 dentry = d_lookup(dir, &nd->last);
> for (;;) {
> 3098 if (!dentry) {
> 3099 dentry = d_alloc_parallel(dir, &nd->last, &wq);
> 3100 if (IS_ERR(dentry))
> 3101 return PTR_ERR(dentry);
> }
> 3103 if (d_in_lookup(dentry))
> break;
>
> error = d_revalidate(dentry, nd->flags);
> 3107 if (likely(error > 0))
> break;
> 3109 if (error)
> goto out_dput;
> 3111 d_invalidate(dentry);
> 3112 dput(dentry);
> dentry = NULL;
> }
> 3115 if (dentry->d_inode) {
> /* Cached positive dentry: will open in f_op->open */
> goto out_no_open;
> }
>
> /*
> * Checking write permission is tricky, bacuse we don't know if we are
> * going to actually need it: O_CREAT opens should work as long as the
> * file exists. But checking existence breaks atomicity. The trick is
> * to check access and if not granted clear O_CREAT from the flags.
> *
> * Another problem is returing the "right" error value (e.g. for an
> * O_EXCL open we want to return EEXIST not EROFS).
> */
> 3129 if (open_flag & O_CREAT) {
> 3130 if (!IS_POSIXACL(dir->d_inode))
> 3131 mode &= ~current_umask();
> 3132 if (unlikely(!got_write)) {
> 3133 create_error = -EROFS;
> 3134 open_flag &= ~O_CREAT;
> 3135 if (open_flag & (O_EXCL | O_TRUNC))
> goto no_open;
> /* No side effects, safe to clear O_CREAT */
> } else {
> 3139 create_error = may_o_create(&nd->path, dentry, mode);
> 3140 if (create_error) {
> 3141 open_flag &= ~O_CREAT;
> 3142 if (open_flag & O_EXCL)
> goto no_open;
> }
> }
> 3146 } else if ((open_flag & (O_TRUNC|O_WRONLY|O_RDWR)) &&
> unlikely(!got_write)) {
> /*
> * No O_CREATE -> atomicity not a requirement -> fall
> * back to lookup + open
> */
> goto no_open;
> }
>
> 3155 if (dir_inode->i_op->atomic_open) {
> error = atomic_open(nd, dentry, path, file, op, open_flag,
> mode, opened);
> 3158 if (unlikely(error == -ENOENT) && create_error)
> error = create_error;
> return error;
> }
>
> no_open:
> 3164 if (d_in_lookup(dentry)) {
> 3165 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
> nd->flags);
> d_lookup_done(dentry);
> 3168 if (unlikely(res)) {
> 3169 if (IS_ERR(res)) {
> error = PTR_ERR(res);
> goto out_dput;
> }
> 3173 dput(dentry);
> dentry = res;
> }
> }
>
> /* Negative dentry, just create the file */
> 3179 if (!dentry->d_inode && (open_flag & O_CREAT)) {
> 3180 *opened |= FILE_CREATED;
> audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
> 3182 if (!dir_inode->i_op->create) {
> 3183 error = -EACCES;
> goto out_dput;
> }
> 3186 error = dir_inode->i_op->create(dir_inode, dentry, mode,
> open_flag & O_EXCL);
> 3188 if (error)
> goto out_dput;
> fsnotify_create(dir_inode, dentry);
> }
> 3192 if (unlikely(create_error) && !dentry->d_inode) {
> error = create_error;
> goto out_dput;
> }
> out_no_open:
> 3197 path->dentry = dentry;
> 3198 path->mnt = nd->path.mnt;
> return 1;
>
> out_dput:
> 3202 dput(dentry);
> return error;
> }
>
> /*
> * Handle the last step of open()
> */
> static int do_last(struct nameidata *nd,
> struct file *file, const struct open_flags *op,
> int *opened)
> {
> 3213 struct dentry *dir = nd->path.dentry;
> 3214 int open_flag = op->open_flag;
> 3215 bool will_truncate = (open_flag & O_TRUNC) != 0;
> 3216 bool got_write = false;
> 3217 int acc_mode = op->acc_mode;
> unsigned seq;
> struct inode *inode;
> struct path path;
> int error;
>
> 3223 nd->flags &= ~LOOKUP_PARENT;
> 3224 nd->flags |= op->intent;
>
> 3226 if (nd->last_type != LAST_NORM) {
> error = handle_dots(nd, nd->last_type);
> if (unlikely(error))
> return error;
> goto finish_open;
> }
>
> 3233 if (!(open_flag & O_CREAT)) {
> 3234 if (nd->last.name[nd->last.len])
> 3235 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
> /* we _can_ be in RCU mode here */
> 3237 error = lookup_fast(nd, &path, &inode, &seq);
> 3238 if (likely(error > 0))
> goto finish_lookup;
>
> 3241 if (error < 0)
> return error;
>
> 3244 BUG_ON(nd->inode != dir->d_inode);
> 3245 BUG_ON(nd->flags & LOOKUP_RCU);
> } else {
> /* create side of things */
> /*
> * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
> * has been cleared when we got to the last component we are
> * about to look up
> */
> 3253 error = complete_walk(nd);
> 3254 if (error)
> return error;
>
> audit_inode(nd->name, dir, LOOKUP_PARENT);
> /* trailing slashes? */
> 3259 if (unlikely(nd->last.name[nd->last.len]))
> return -EISDIR;
> }
>
> 3263 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
> 3264 error = mnt_want_write(nd->path.mnt);
> 3265 if (!error)
> got_write = true;
> /*
> * do _not_ fail yet - we might not need that or fail with
> * a different error; let lookup_open() decide; we'll be
> * dropping this one anyway.
> */
> }
> if (open_flag & O_CREAT)
> inode_lock(dir->d_inode);
> else
> inode_lock_shared(dir->d_inode);
> error = lookup_open(nd, &path, file, op, got_write, opened);
> 3278 if (open_flag & O_CREAT)
> inode_unlock(dir->d_inode);
> else
> inode_unlock_shared(dir->d_inode);
>
> 3283 if (error <= 0) {
> 3284 if (error)
> goto out;
>
> 3287 if ((*opened & FILE_CREATED) ||
> 3288 !S_ISREG(file_inode(file)->i_mode))
> will_truncate = false;
>
> audit_inode(nd->name, file->f_path.dentry, 0);
> goto opened;
> }
>
> 3295 if (*opened & FILE_CREATED) {
> /* Don't check for write permission, don't truncate */
> 3297 open_flag &= ~O_TRUNC;
> 3298 will_truncate = false;
> 3299 acc_mode = 0;
> path_to_nameidata(&path, nd);
> goto finish_open_created;
> }
>
> /*
> * If atomic_open() acquired write access it is dropped now due to
> * possible mount and symlink following (this might be optimized away if
> * necessary...)
> */
> 3309 if (got_write) {
> 3310 mnt_drop_write(nd->path.mnt);
> got_write = false;
> }
>
> 3314 error = follow_managed(&path, nd);
> 3315 if (unlikely(error < 0))
> return error;
>
> 3318 if (unlikely(d_is_negative(path.dentry))) {
> path_to_nameidata(&path, nd);
> return -ENOENT;
> }
>
> /*
> * create/update audit record if it already exists.
> */
> audit_inode(nd->name, path.dentry, 0);
>
> 3328 if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
> path_to_nameidata(&path, nd);
> 3330 return -EEXIST;
> }
>
> 3333 seq = 0; /* out of RCU mode, so the value doesn't matter */
> 3334 inode = d_backing_inode(path.dentry);
> finish_lookup:
> error = step_into(nd, &path, 0, inode, seq);
> 3337 if (unlikely(error))
> return error;
> finish_open:
> /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
> 3341 error = complete_walk(nd);
> 3342 if (error)
> return error;
> 3344 audit_inode(nd->name, nd->path.dentry, 0);
> 3345 error = -EISDIR;
> 3346 if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
> goto out;
> 3348 error = -ENOTDIR;
> 3349 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
> goto out;
> 3351 if (!d_is_reg(nd->path.dentry))
> 3352 will_truncate = false;
>
> 3354 if (will_truncate) {
> 3355 error = mnt_want_write(nd->path.mnt);
> 3356 if (error)
> goto out;
> 3358 got_write = true;
> }
> finish_open_created:
> 3361 error = may_open(&nd->path, acc_mode, open_flag);
> 3362 if (error)
> goto out;
> 3364 BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
> 3365 error = vfs_open(&nd->path, file, current_cred());
> 3366 if (error)
> goto out;
> 3368 *opened |= FILE_OPENED;
> opened:
> error = ima_file_check(file, op->acc_mode, *opened);
> 3371 if (!error && will_truncate)
> error = handle_truncate(file);
> out:
> 3374 if (unlikely(error) && (*opened & FILE_OPENED))
> 3375 fput(file);
> 3376 if (unlikely(error > 0)) {
> 3377 WARN_ON(1);
> 3378 error = -EINVAL;
> }
> 3380 if (got_write)
> 3381 mnt_drop_write(nd->path.mnt);
> return error;
> }
>
> struct dentry *vfs_tmpfile(struct dentry *dentry, umode_t mode, int open_flag)
> 3386 {
> 3387 struct dentry *child = NULL;
> 3388 struct inode *dir = dentry->d_inode;
> struct inode *inode;
> int error;
>
> /* we want directory to be writable */
> 3393 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
> 3394 if (error)
> goto out_err;
> error = -EOPNOTSUPP;
> 3397 if (!dir->i_op->tmpfile)
> goto out_err;
> error = -ENOMEM;
> 3400 child = d_alloc(dentry, &slash_name);
> 3401 if (unlikely(!child))
> goto out_err;
> 3403 error = dir->i_op->tmpfile(dir, child, mode);
> 3404 if (error)
> goto out_err;
> error = -ENOENT;
> 3407 inode = child->d_inode;
> 3408 if (unlikely(!inode))
> goto out_err;
> 3410 if (!(open_flag & O_EXCL)) {
> spin_lock(&inode->i_lock);
> 3412 inode->i_state |= I_LINKABLE;
> spin_unlock(&inode->i_lock);
> }
> return child;
>
> 3417 out_err:
> 3418 dput(child);
> return ERR_PTR(error);
> 3420 }
> EXPORT_SYMBOL(vfs_tmpfile);
>
> static int do_tmpfile(struct nameidata *nd, unsigned flags,
> const struct open_flags *op,
> struct file *file, int *opened)
> {
> struct dentry *child;
> struct path path;
> 3429 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
> 3430 if (unlikely(error))
> return error;
> 3432 error = mnt_want_write(path.mnt);
> 3433 if (unlikely(error))
> goto out;
> 3435 child = vfs_tmpfile(path.dentry, op->mode, op->open_flag);
> 3436 error = PTR_ERR(child);
> 3437 if (IS_ERR(child))
> goto out2;
> 3439 dput(path.dentry);
> 3440 path.dentry = child;
> audit_inode(nd->name, child, 0);
> /* Don't check for other permissions, the inode was just created */
> 3443 error = may_open(&path, 0, op->open_flag);
> 3444 if (error)
> goto out2;
> 3446 file->f_path.mnt = path.mnt;
> 3447 error = finish_open(file, child, NULL, opened);
> if (error)
> goto out2;
> out2:
> 3451 mnt_drop_write(path.mnt);
> out:
> path_put(&path);
> return error;
> }
>
> static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
> {
> struct path path;
> 3460 int error = path_lookupat(nd, flags, &path);
> 3461 if (!error) {
> audit_inode(nd->name, path.dentry, 0);
> 3463 error = vfs_open(&path, file, current_cred());
> path_put(&path);
> }
> return error;
> }
>
> static struct file *path_openat(struct nameidata *nd,
> const struct open_flags *op, unsigned flags)
> 3471 {
> const char *s;
> struct file *file;
> 3474 int opened = 0;
> int error;
>
> 3477 file = get_empty_filp();
> 3478 if (IS_ERR(file))
> return file;
>
> 3481 file->f_flags = op->open_flag;
>
> 3483 if (unlikely(file->f_flags & __O_TMPFILE)) {
> error = do_tmpfile(nd, flags, op, file, &opened);
> 3485 goto out2;
> }
>
> 3488 if (unlikely(file->f_flags & O_PATH)) {
> error = do_o_path(nd, flags, file);
> 3490 if (!error)
> opened |= FILE_OPENED;
> goto out2;
> }
>
> 3495 s = path_init(nd, flags);
> 3496 if (IS_ERR(s)) {
> 3497 put_filp(file);
> 3498 return ERR_CAST(s);
> }
> 3500 while (!(error = link_path_walk(s, nd)) &&
> (error = do_last(nd, file, op, &opened)) > 0) {
> 3502 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
> 3503 s = trailing_symlink(nd);
> 3504 if (IS_ERR(s)) {
> 3505 error = PTR_ERR(s);
> break;
> }
> }
> 3509 terminate_walk(nd);
> out2:
> 3511 if (!(opened & FILE_OPENED)) {
> 3512 BUG_ON(!error);
> 3513 put_filp(file);
> }
> 3515 if (unlikely(error)) {
> 3516 if (error == -EOPENSTALE) {
> 3517 if (flags & LOOKUP_RCU)
> error = -ECHILD;
> else
> error = -ESTALE;
> }
> file = ERR_PTR(error);
> }
> return file;
> 3525 }
>
> struct file *do_filp_open(int dfd, struct filename *pathname,
> const struct open_flags *op)
> 3529 {
> struct nameidata nd;
> 3531 int flags = op->lookup_flags;
> struct file *filp;
>
> set_nameidata(&nd, dfd, pathname);
> 3535 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
> 3536 if (unlikely(filp == ERR_PTR(-ECHILD)))
> 3537 filp = path_openat(&nd, op, flags);
> 3538 if (unlikely(filp == ERR_PTR(-ESTALE)))
> 3539 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
> 3540 restore_nameidata();
> return filp;
> 3542 }
>
> struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
> const char *name, const struct open_flags *op)
> 3546 {
> struct nameidata nd;
> struct file *file;
> struct filename *filename;
> 3550 int flags = op->lookup_flags | LOOKUP_ROOT;
>
> 3552 nd.root.mnt = mnt;
> 3553 nd.root.dentry = dentry;
>
> 3555 if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
> 3556 return ERR_PTR(-ELOOP);
>
> 3558 filename = getname_kernel(name);
> 3559 if (IS_ERR(filename))
> 3560 return ERR_CAST(filename);
>
> set_nameidata(&nd, -1, filename);
> 3563 file = path_openat(&nd, op, flags | LOOKUP_RCU);
> 3564 if (unlikely(file == ERR_PTR(-ECHILD)))
> 3565 file = path_openat(&nd, op, flags);
> 3566 if (unlikely(file == ERR_PTR(-ESTALE)))
> 3567 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
> 3568 restore_nameidata();
> 3569 putname(filename);
> return file;
> 3571 }
>
> static struct dentry *filename_create(int dfd, struct filename *name,
> struct path *path, unsigned int lookup_flags)
> 3575 {
> 3576 struct dentry *dentry = ERR_PTR(-EEXIST);
> struct qstr last;
> int type;
> int err2;
> int error;
> bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
>
> /*
> * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
> * other flags passed in are ignored!
> */
> 3587 lookup_flags &= LOOKUP_REVAL;
>
> 3589 name = filename_parentat(dfd, name, lookup_flags, path, &last, &type);
> 3590 if (IS_ERR(name))
> 3591 return ERR_CAST(name);
>
> /*
> * Yucky last component or no last component at all?
> * (foo/., foo/.., /////)
> */
> 3597 if (unlikely(type != LAST_NORM))
> goto out;
>
> /* don't fail immediately if it's r/o, at least try to report other errors */
> 3601 err2 = mnt_want_write(path->mnt);
> /*
> * Do the final lookup.
> */
> 3605 lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
> 3606 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
> 3607 dentry = __lookup_hash(&last, path->dentry, lookup_flags);
> 3608 if (IS_ERR(dentry))
> goto unlock;
>
> error = -EEXIST;
> 3612 if (d_is_positive(dentry))
> goto fail;
>
> /*
> * Special case - lookup gave negative, but... we had foo/bar/
> * From the vfs_mknod() POV we just have a negative dentry -
> * all is fine. Let's be bastards - you had / on the end, you've
> * been asking for (non-existent) directory. -ENOENT for you.
> */
> 3621 if (unlikely(!is_dir && last.name[last.len])) {
> error = -ENOENT;
> goto fail;
> }
> 3625 if (unlikely(err2)) {
> error = err2;
> goto fail;
> }
> putname(name);
> return dentry;
> 3631 fail:
> 3632 dput(dentry);
> 3633 dentry = ERR_PTR(error);
> unlock:
> 3635 inode_unlock(path->dentry->d_inode);
> 3636 if (!err2)
> 3637 mnt_drop_write(path->mnt);
> out:
> path_put(path);
> 3640 putname(name);
> return dentry;
> 3642 }
>
> struct dentry *kern_path_create(int dfd, const char *pathname,
> struct path *path, unsigned int lookup_flags)
> 3646 {
> 3647 return filename_create(dfd, getname_kernel(pathname),
> path, lookup_flags);
> 3649 }
> EXPORT_SYMBOL(kern_path_create);
>
> void done_path_create(struct path *path, struct dentry *dentry)
> 3653 {
> 3654 dput(dentry);
> 3655 inode_unlock(path->dentry->d_inode);
> 3656 mnt_drop_write(path->mnt);
> path_put(path);
> 3658 }
> EXPORT_SYMBOL(done_path_create);
>
> inline struct dentry *user_path_create(int dfd, const char __user *pathname,
> struct path *path, unsigned int lookup_flags)
> 3663 {
> 3664 return filename_create(dfd, getname(pathname), path, lookup_flags);
> 3665 }
> EXPORT_SYMBOL(user_path_create);
>
> int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
> 3669 {
> int error = may_create(dir, dentry);
>
> 3672 if (error)
> return error;
>
> 3675 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
> 3676 return -EPERM;
>
> 3678 if (!dir->i_op->mknod)
> return -EPERM;
>
> error = devcgroup_inode_mknod(mode, dev);
> 3682 if (error)
> return error;
>
> 3685 error = security_inode_mknod(dir, dentry, mode, dev);
> 3686 if (error)
> return error;
>
> 3689 error = dir->i_op->mknod(dir, dentry, mode, dev);
> 3690 if (!error)
> fsnotify_create(dir, dentry);
> return error;
> 3693 }
> EXPORT_SYMBOL(vfs_mknod);
>
> static int may_mknod(umode_t mode)
> {
> 3698 switch (mode & S_IFMT) {
> case S_IFREG:
> case S_IFCHR:
> case S_IFBLK:
> case S_IFIFO:
> case S_IFSOCK:
> case 0: /* zero mode translates to S_IFREG */
> return 0;
> case S_IFDIR:
> return -EPERM;
> default:
> return -EINVAL;
> }
> }
>
> long do_mknodat(int dfd, const char __user *filename, umode_t mode,
> unsigned int dev)
> 3715 {
> struct dentry *dentry;
> struct path path;
> int error;
> 3719 unsigned int lookup_flags = 0;
>
> error = may_mknod(mode);
> if (error)
> return error;
> retry:
> dentry = user_path_create(dfd, filename, &path, lookup_flags);
> 3726 if (IS_ERR(dentry))
> return PTR_ERR(dentry);
>
> 3729 if (!IS_POSIXACL(path.dentry->d_inode))
> 3730 mode &= ~current_umask();
> 3731 error = security_path_mknod(&path, dentry, mode, dev);
> if (error)
> goto out;
> 3734 switch (mode & S_IFMT) {
> case 0: case S_IFREG:
> 3736 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
> if (!error)
> ima_post_path_mknod(dentry);
> break;
> case S_IFCHR: case S_IFBLK:
> 3741 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
> new_decode_dev(dev));
> break;
> case S_IFIFO: case S_IFSOCK:
> 3745 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
> break;
> }
> out:
> 3749 done_path_create(&path, dentry);
> 3750 if (retry_estale(error, lookup_flags)) {
> 3751 lookup_flags |= LOOKUP_REVAL;
> goto retry;
> }
> return error;
> 3755 }
>
> 3757 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
> unsigned int, dev)
> {
> 3760 return do_mknodat(dfd, filename, mode, dev);
> }
>
> 3763 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
> {
> 3765 return do_mknodat(AT_FDCWD, filename, mode, dev);
> }
>
> int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
> 3769 {
> int error = may_create(dir, dentry);
> 3771 unsigned max_links = dir->i_sb->s_max_links;
>
> 3773 if (error)
> return error;
>
> 3776 if (!dir->i_op->mkdir)
> 3777 return -EPERM;
>
> mode &= (S_IRWXUGO|S_ISVTX);
> 3780 error = security_inode_mkdir(dir, dentry, mode);
> 3781 if (error)
> return error;
>
> 3784 if (max_links && dir->i_nlink >= max_links)
> 3785 return -EMLINK;
>
> 3787 error = dir->i_op->mkdir(dir, dentry, mode);
> 3788 if (!error)
> fsnotify_mkdir(dir, dentry);
> return error;
> 3791 }
> EXPORT_SYMBOL(vfs_mkdir);
>
> long do_mkdirat(int dfd, const char __user *pathname, umode_t mode)
> 3795 {
> struct dentry *dentry;
> struct path path;
> int error;
> 3799 unsigned int lookup_flags = LOOKUP_DIRECTORY;
>
> retry:
> dentry = user_path_create(dfd, pathname, &path, lookup_flags);
> 3803 if (IS_ERR(dentry))
> return PTR_ERR(dentry);
>
> 3806 if (!IS_POSIXACL(path.dentry->d_inode))
> 3807 mode &= ~current_umask();
> 3808 error = security_path_mkdir(&path, dentry, mode);
> if (!error)
> 3810 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
> 3811 done_path_create(&path, dentry);
> 3812 if (retry_estale(error, lookup_flags)) {
> 3813 lookup_flags |= LOOKUP_REVAL;
> goto retry;
> }
> return error;
> 3817 }
>
> 3819 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
> {
> 3821 return do_mkdirat(dfd, pathname, mode);
> }
>
> 3824 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
> {
> 3826 return do_mkdirat(AT_FDCWD, pathname, mode);
> }
>
> int vfs_rmdir(struct inode *dir, struct dentry *dentry)
> 3830 {
> 3831 int error = may_delete(dir, dentry, 1);
>
> 3833 if (error)
> return error;
>
> 3836 if (!dir->i_op->rmdir)
> 3837 return -EPERM;
>
> dget(dentry);
> inode_lock(dentry->d_inode);
>
> 3842 error = -EBUSY;
> 3843 if (is_local_mountpoint(dentry))
> goto out;
>
> 3846 error = security_inode_rmdir(dir, dentry);
> 3847 if (error)
> goto out;
>
> 3850 shrink_dcache_parent(dentry);
> 3851 error = dir->i_op->rmdir(dir, dentry);
> 3852 if (error)
> goto out;
>
> 3855 dentry->d_inode->i_flags |= S_DEAD;
> dont_mount(dentry);
> detach_mounts(dentry);
>
> out:
> inode_unlock(dentry->d_inode);
> 3861 dput(dentry);
> if (!error)
> 3863 d_delete(dentry);
> return error;
> 3865 }
> EXPORT_SYMBOL(vfs_rmdir);
>
> long do_rmdir(int dfd, const char __user *pathname)
> 3869 {
> int error = 0;
> struct filename *name;
> struct dentry *dentry;
> struct path path;
> struct qstr last;
> int type;
> 3876 unsigned int lookup_flags = 0;
> retry:
> 3878 name = filename_parentat(dfd, getname(pathname), lookup_flags,
> &path, &last, &type);
> 3880 if (IS_ERR(name))
> 3881 return PTR_ERR(name);
>
> 3883 switch (type) {
> case LAST_DOTDOT:
> error = -ENOTEMPTY;
> goto exit1;
> case LAST_DOT:
> error = -EINVAL;
> goto exit1;
> case LAST_ROOT:
> error = -EBUSY;
> goto exit1;
> }
>
> 3895 error = mnt_want_write(path.mnt);
> 3896 if (error)
> goto exit1;
>
> 3899 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
> 3900 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
> error = PTR_ERR(dentry);
> 3902 if (IS_ERR(dentry))
> goto exit2;
> 3904 if (!dentry->d_inode) {
> error = -ENOENT;
> goto exit3;
> }
> error = security_path_rmdir(&path, dentry);
> if (error)
> goto exit3;
> 3911 error = vfs_rmdir(path.dentry->d_inode, dentry);
> exit3:
> 3913 dput(dentry);
> exit2:
> 3915 inode_unlock(path.dentry->d_inode);
> 3916 mnt_drop_write(path.mnt);
> exit1:
> path_put(&path);
> 3919 putname(name);
> if (retry_estale(error, lookup_flags)) {
> 3921 lookup_flags |= LOOKUP_REVAL;
> goto retry;
> }
> return error;
> 3925 }
>
> 3927 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
> {
> 3929 return do_rmdir(AT_FDCWD, pathname);
> }
>
> /**
> * vfs_unlink - unlink a filesystem object
> * @dir: parent directory
> * @dentry: victim
> * @delegated_inode: returns victim inode, if the inode is delegated.
> *
> * The caller must hold dir->i_mutex.
> *
> * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
> * return a reference to the inode in delegated_inode. The caller
> * should then break the delegation on that inode and retry. Because
> * breaking a delegation may take a long time, the caller should drop
> * dir->i_mutex before doing so.
> *
> * Alternatively, a caller may pass NULL for delegated_inode. This may
> * be appropriate for callers that expect the underlying filesystem not
> * to be NFS exported.
> */
> int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode)
> 3951 {
> 3952 struct inode *target = dentry->d_inode;
> 3953 int error = may_delete(dir, dentry, 0);
>
> 3955 if (error)
> return error;
>
> 3958 if (!dir->i_op->unlink)
> 3959 return -EPERM;
>
> inode_lock(target);
> 3962 if (is_local_mountpoint(dentry))
> 3963 error = -EBUSY;
> else {
> 3965 error = security_inode_unlink(dir, dentry);
> 3966 if (!error) {
> error = try_break_deleg(target, delegated_inode);
> 3968 if (error)
> goto out;
> 3970 error = dir->i_op->unlink(dir, dentry);
> 3971 if (!error) {
> dont_mount(dentry);
> detach_mounts(dentry);
> }
> }
> }
> out:
> inode_unlock(target);
>
> /* We don't d_delete() NFS sillyrenamed files--they still exist. */
> 3981 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
> fsnotify_link_count(target);
> 3983 d_delete(dentry);
> }
>
> return error;
> 3987 }
> EXPORT_SYMBOL(vfs_unlink);
>
> /*
> * Make sure that the actual truncation of the file will occur outside its
> * directory's i_mutex. Truncate can take a long time if there is a lot of
> * writeout happening, and we don't want to prevent access to the directory
> * while waiting on the I/O.
> */
> long do_unlinkat(int dfd, struct filename *name)
> 3997 {
> int error;
> struct dentry *dentry;
> struct path path;
> struct qstr last;
> int type;
> struct inode *inode = NULL;
> 4004 struct inode *delegated_inode = NULL;
> 4005 unsigned int lookup_flags = 0;
> retry:
> 4007 name = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
> 4008 if (IS_ERR(name))
> 4009 return PTR_ERR(name);
>
> error = -EISDIR;
> 4012 if (type != LAST_NORM)
> goto exit1;
>
> 4015 error = mnt_want_write(path.mnt);
> 4016 if (error)
> goto exit1;
> retry_deleg:
> 4019 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
> 4020 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
> 4021 error = PTR_ERR(dentry);
> 4022 if (!IS_ERR(dentry)) {
> /* Why not before? Because we want correct error value */
> 4024 if (last.name[last.len])
> goto slashes;
> 4026 inode = dentry->d_inode;
> 4027 if (d_is_negative(dentry))
> goto slashes;
> 4029 ihold(inode);
> error = security_path_unlink(&path, dentry);
> if (error)
> goto exit2;
> 4033 error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode);
> exit2:
> 4035 dput(dentry);
> }
> 4037 inode_unlock(path.dentry->d_inode);
> 4038 if (inode)
> 4039 iput(inode); /* truncate the inode here */
> inode = NULL;
> 4041 if (delegated_inode) {
> error = break_deleg_wait(&delegated_inode);
> 4043 if (!error)
> goto retry_deleg;
> }
> 4046 mnt_drop_write(path.mnt);
> exit1:
> path_put(&path);
> 4049 if (retry_estale(error, lookup_flags)) {
> 4050 lookup_flags |= LOOKUP_REVAL;
> inode = NULL;
> goto retry;
> }
> 4054 putname(name);
> return error;
>
> slashes:
> 4058 if (d_is_negative(dentry))
> 4059 error = -ENOENT;
> else if (d_is_dir(dentry))
> 4061 error = -EISDIR;
> else
> 4063 error = -ENOTDIR;
> goto exit2;
> 4065 }
>
> 4067 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
> {
> 4069 if ((flag & ~AT_REMOVEDIR) != 0)
> return -EINVAL;
>
> 4072 if (flag & AT_REMOVEDIR)
> 4073 return do_rmdir(dfd, pathname);
>
> 4075 return do_unlinkat(dfd, getname(pathname));
> }
>
> 4078 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
> {
> 4080 return do_unlinkat(AT_FDCWD, getname(pathname));
> }
>
> int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
> 4084 {
> int error = may_create(dir, dentry);
>
> 4087 if (error)
> return error;
>
> 4090 if (!dir->i_op->symlink)
> 4091 return -EPERM;
>
> 4093 error = security_inode_symlink(dir, dentry, oldname);
> 4094 if (error)
> return error;
>
> 4097 error = dir->i_op->symlink(dir, dentry, oldname);
> 4098 if (!error)
> fsnotify_create(dir, dentry);
> return error;
> 4101 }
> EXPORT_SYMBOL(vfs_symlink);
>
> long do_symlinkat(const char __user *oldname, int newdfd,
> const char __user *newname)
> 4106 {
> int error;
> struct filename *from;
> struct dentry *dentry;
> struct path path;
> unsigned int lookup_flags = 0;
>
> from = getname(oldname);
> 4114 if (IS_ERR(from))
> return PTR_ERR(from);
> retry:
> dentry = user_path_create(newdfd, newname, &path, lookup_flags);
> 4118 error = PTR_ERR(dentry);
> 4119 if (IS_ERR(dentry))
> goto out_putname;
>
> error = security_path_symlink(&path, dentry, from->name);
> if (!error)
> 4124 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
> 4125 done_path_create(&path, dentry);
> if (retry_estale(error, lookup_flags)) {
> 4127 lookup_flags |= LOOKUP_REVAL;
> goto retry;
> }
> out_putname:
> 4131 putname(from);
> 4132 return error;
> 4133 }
>
> 4135 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
> int, newdfd, const char __user *, newname)
> {
> 4138 return do_symlinkat(oldname, newdfd, newname);
> }
>
> 4141 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
> {
> 4143 return do_symlinkat(oldname, AT_FDCWD, newname);
> }
>
> /**
> * vfs_link - create a new link
> * @old_dentry: object to be linked
> * @dir: new parent
> * @new_dentry: where to create the new link
> * @delegated_inode: returns inode needing a delegation break
> *
> * The caller must hold dir->i_mutex
> *
> * If vfs_link discovers a delegation on the to-be-linked file in need
> * of breaking, it will return -EWOULDBLOCK and return a reference to the
> * inode in delegated_inode. The caller should then break the delegation
> * and retry. Because breaking a delegation may take a long time, the
> * caller should drop the i_mutex before doing so.
> *
> * Alternatively, a caller may pass NULL for delegated_inode. This may
> * be appropriate for callers that expect the underlying filesystem not
> * to be NFS exported.
> */
> int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
> 4166 {
> 4167 struct inode *inode = old_dentry->d_inode;
> 4168 unsigned max_links = dir->i_sb->s_max_links;
> int error;
>
> 4171 if (!inode)
> return -ENOENT;
>
> error = may_create(dir, new_dentry);
> 4175 if (error)
> return error;
>
> 4178 if (dir->i_sb != inode->i_sb)
> 4179 return -EXDEV;
>
> /*
> * A link to an append-only or immutable file cannot be created.
> */
> 4184 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
> 4185 return -EPERM;
> /*
> * Updating the link count will likely cause i_uid and i_gid to
> * be writen back improperly if their true value is unknown to
> * the vfs.
> */
> if (HAS_UNMAPPED_ID(inode))
> return -EPERM;
> 4193 if (!dir->i_op->link)
> return -EPERM;
> 4195 if (S_ISDIR(inode->i_mode))
> return -EPERM;
>
> 4198 error = security_inode_link(old_dentry, dir, new_dentry);
> 4199 if (error)
> return error;
>
> inode_lock(inode);
> /* Make sure we don't allow creating hardlink to an unlinked file */
> 4204 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
> 4205 error = -ENOENT;
> 4206 else if (max_links && inode->i_nlink >= max_links)
> 4207 error = -EMLINK;
> else {
> error = try_break_deleg(inode, delegated_inode);
> 4210 if (!error)
> 4211 error = dir->i_op->link(old_dentry, dir, new_dentry);
> }
>
> 4214 if (!error && (inode->i_state & I_LINKABLE)) {
> spin_lock(&inode->i_lock);
> 4216 inode->i_state &= ~I_LINKABLE;
> spin_unlock(&inode->i_lock);
> }
> inode_unlock(inode);
> if (!error)
> fsnotify_link(dir, inode, new_dentry);
> return error;
> 4223 }
> EXPORT_SYMBOL(vfs_link);
>
> /*
> * Hardlinks are often used in delicate situations. We avoid
> * security-related surprises by not following symlinks on the
> * newname. --KAB
> *
> * We don't follow them on the oldname either to be compatible
> * with linux 2.0, and to avoid hard-linking to directories
> * and other special files. --ADM
> */
> int do_linkat(int olddfd, const char __user *oldname, int newdfd,
> const char __user *newname, int flags)
> 4237 {
> struct dentry *new_dentry;
> struct path old_path, new_path;
> 4240 struct inode *delegated_inode = NULL;
> int how = 0;
> int error;
>
> 4244 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
> 4245 return -EINVAL;
> /*
> * To use null names we require CAP_DAC_READ_SEARCH
> * This ensures that not everyone will be able to create
> * handlink using the passed filedescriptor.
> */
> 4251 if (flags & AT_EMPTY_PATH) {
> 4252 if (!capable(CAP_DAC_READ_SEARCH))
> 4253 return -ENOENT;
> 4254 how = LOOKUP_EMPTY;
> }
>
> if (flags & AT_SYMLINK_FOLLOW)
> 4258 how |= LOOKUP_FOLLOW;
> retry:
> error = user_path_at(olddfd, oldname, how, &old_path);
> 4261 if (error)
> return error;
>
> 4264 new_dentry = user_path_create(newdfd, newname, &new_path,
> (how & LOOKUP_REVAL));
> error = PTR_ERR(new_dentry);
> 4267 if (IS_ERR(new_dentry))
> goto out;
>
> 4270 error = -EXDEV;
> 4271 if (old_path.mnt != new_path.mnt)
> goto out_dput;
> error = may_linkat(&old_path);
> if (unlikely(error))
> goto out_dput;
> error = security_path_link(old_path.dentry, &new_path, new_dentry);
> if (error)
> goto out_dput;
> 4279 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode);
> out_dput:
> 4281 done_path_create(&new_path, new_dentry);
> 4282 if (delegated_inode) {
> error = break_deleg_wait(&delegated_inode);
> 4284 if (!error) {
> path_put(&old_path);
> goto retry;
> }
> }
> if (retry_estale(error, how)) {
> path_put(&old_path);
> 4291 how |= LOOKUP_REVAL;
> 4292 goto retry;
> }
> out:
> path_put(&old_path);
>
> 4297 return error;
> 4298 }
>
> 4300 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
> int, newdfd, const char __user *, newname, int, flags)
> {
> 4303 return do_linkat(olddfd, oldname, newdfd, newname, flags);
> }
>
> 4306 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
> {
> 4308 return do_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
> }
>
> /**
> * vfs_rename - rename a filesystem object
> * @old_dir: parent of source
> * @old_dentry: source
> * @new_dir: parent of destination
> * @new_dentry: destination
> * @delegated_inode: returns an inode needing a delegation break
> * @flags: rename flags
> *
> * The caller must hold multiple mutexes--see lock_rename()).
> *
> * If vfs_rename discovers a delegation in need of breaking at either
> * the source or destination, it will return -EWOULDBLOCK and return a
> * reference to the inode in delegated_inode. The caller should then
> * break the delegation and retry. Because breaking a delegation may
> * take a long time, the caller should drop all locks before doing
> * so.
> *
> * Alternatively, a caller may pass NULL for delegated_inode. This may
> * be appropriate for callers that expect the underlying filesystem not
> * to be NFS exported.
> *
> * The worst of all namespace operations - renaming directory. "Perverted"
> * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
> * Problems:
> *
> * a) we can get into loop creation.
> * b) race potential - two innocent renames can create a loop together.
> * That's where 4.4 screws up. Current fix: serialization on
> * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
> * story.
> * c) we have to lock _four_ objects - parents and victim (if it exists),
> * and source (if it is not a directory).
> * And that - after we got ->i_mutex on parents (until then we don't know
> * whether the target exists). Solution: try to be smart with locking
> * order for inodes. We rely on the fact that tree topology may change
> * only under ->s_vfs_rename_mutex _and_ that parent of the object we
> * move will be locked. Thus we can rank directories by the tree
> * (ancestors first) and rank all non-directories after them.
> * That works since everybody except rename does "lock parent, lookup,
> * lock child" and rename is under ->s_vfs_rename_mutex.
> * HOWEVER, it relies on the assumption that any object with ->lookup()
> * has no more than 1 dentry. If "hybrid" objects will ever appear,
> * we'd better make sure that there's no link(2) for them.
> * d) conversion from fhandle to dentry may come in the wrong moment - when
> * we are removing the target. Solution: we will have to grab ->i_mutex
> * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
> * ->i_mutex on parents, which works but leads to some truly excessive
> * locking].
> */
> int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
> struct inode *new_dir, struct dentry *new_dentry,
> struct inode **delegated_inode, unsigned int flags)
> 4364 {
> int error;
> bool is_dir = d_is_dir(old_dentry);
> 4367 struct inode *source = old_dentry->d_inode;
> 4368 struct inode *target = new_dentry->d_inode;
> 4369 bool new_is_dir = false;
> 4370 unsigned max_links = new_dir->i_sb->s_max_links;
> struct name_snapshot old_name;
>
> 4373 if (source == target)
> 4374 return 0;
>
> 4376 error = may_delete(old_dir, old_dentry, is_dir);
> 4377 if (error)
> return error;
>
> 4380 if (!target) {
> error = may_create(new_dir, new_dentry);
> } else {
> new_is_dir = d_is_dir(new_dentry);
>
> 4385 if (!(flags & RENAME_EXCHANGE))
> 4386 error = may_delete(new_dir, new_dentry, is_dir);
> else
> 4388 error = may_delete(new_dir, new_dentry, new_is_dir);
> }
> 4390 if (error)
> return error;
>
> 4393 if (!old_dir->i_op->rename)
> 4394 return -EPERM;
>
> /*
> * If we are going to change the parent - check write permissions,
> * we'll need to flip '..'.
> */
> 4400 if (new_dir != old_dir) {
> 4401 if (is_dir) {
> 4402 error = inode_permission(source, MAY_WRITE);
> 4403 if (error)
> return error;
> }
> 4406 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
> 4407 error = inode_permission(target, MAY_WRITE);
> 4408 if (error)
> return error;
> }
> }
>
> 4413 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
> flags);
> 4415 if (error)
> return error;
>
> 4418 take_dentry_name_snapshot(&old_name, old_dentry);
> dget(new_dentry);
> 4420 if (!is_dir || (flags & RENAME_EXCHANGE))
> 4421 lock_two_nondirectories(source, target);
> 4422 else if (target)
> inode_lock(target);
>
> 4425 error = -EBUSY;
> 4426 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
> goto out;
>
> 4429 if (max_links && new_dir != old_dir) {
> 4430 error = -EMLINK;
> 4431 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
> goto out;
> 4433 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
> old_dir->i_nlink >= max_links)
> goto out;
> }
> 4437 if (is_dir && !(flags & RENAME_EXCHANGE) && target)
> 4438 shrink_dcache_parent(new_dentry);
> if (!is_dir) {
> error = try_break_deleg(source, delegated_inode);
> 4441 if (error)
> goto out;
> }
> 4444 if (target && !new_is_dir) {
> error = try_break_deleg(target, delegated_inode);
> 4446 if (error)
> goto out;
> }
> 4449 error = old_dir->i_op->rename(old_dir, old_dentry,
> new_dir, new_dentry, flags);
> 4451 if (error)
> goto out;
>
> 4454 if (!(flags & RENAME_EXCHANGE) && target) {
> 4455 if (is_dir)
> 4456 target->i_flags |= S_DEAD;
> dont_mount(new_dentry);
> detach_mounts(new_dentry);
> }
> 4460 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
> if (!(flags & RENAME_EXCHANGE))
> 4462 d_move(old_dentry, new_dentry);
> else
> 4464 d_exchange(old_dentry, new_dentry);
> }
> out:
> 4467 if (!is_dir || (flags & RENAME_EXCHANGE))
> 4468 unlock_two_nondirectories(source, target);
> 4469 else if (target)
> inode_unlock(target);
> 4471 dput(new_dentry);
> if (!error) {
> 4473 fsnotify_move(old_dir, new_dir, old_name.name, is_dir,
> 4474 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
> 4475 if (flags & RENAME_EXCHANGE) {
> 4476 fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
> new_is_dir, NULL, new_dentry);
> }
> }
> 4480 release_dentry_name_snapshot(&old_name);
>
> 4482 return error;
> 4483 }
> EXPORT_SYMBOL(vfs_rename);
>
> static int do_renameat2(int olddfd, const char __user *oldname, int newdfd,
> const char __user *newname, unsigned int flags)
> 4488 {
> struct dentry *old_dentry, *new_dentry;
> struct dentry *trap;
> struct path old_path, new_path;
> struct qstr old_last, new_last;
> int old_type, new_type;
> 4494 struct inode *delegated_inode = NULL;
> struct filename *from;
> struct filename *to;
> 4497 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
> bool should_retry = false;
> int error;
>
> 4501 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
> 4502 return -EINVAL;
>
> 4504 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
> (flags & RENAME_EXCHANGE))
> return -EINVAL;
>
> 4508 if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
> 4509 return -EPERM;
>
> 4511 if (flags & RENAME_EXCHANGE)
> target_flags = 0;
>
> 4514 retry:
> 4515 from = filename_parentat(olddfd, getname(oldname), lookup_flags,
> &old_path, &old_last, &old_type);
> 4517 if (IS_ERR(from)) {
> 4518 error = PTR_ERR(from);
> 4519 goto exit;
> }
>
> 4522 to = filename_parentat(newdfd, getname(newname), lookup_flags,
> &new_path, &new_last, &new_type);
> 4524 if (IS_ERR(to)) {
> 4525 error = PTR_ERR(to);
> goto exit1;
> }
>
> 4529 error = -EXDEV;
> 4530 if (old_path.mnt != new_path.mnt)
> goto exit2;
>
> 4533 error = -EBUSY;
> 4534 if (old_type != LAST_NORM)
> goto exit2;
>
> 4537 if (flags & RENAME_NOREPLACE)
> 4538 error = -EEXIST;
> 4539 if (new_type != LAST_NORM)
> goto exit2;
>
> 4542 error = mnt_want_write(old_path.mnt);
> 4543 if (error)
> goto exit2;
>
> retry_deleg:
> 4547 trap = lock_rename(new_path.dentry, old_path.dentry);
>
> 4549 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags);
> 4550 error = PTR_ERR(old_dentry);
> 4551 if (IS_ERR(old_dentry))
> goto exit3;
> /* source must exist */
> 4554 error = -ENOENT;
> 4555 if (d_is_negative(old_dentry))
> goto exit4;
> 4557 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags);
> 4558 error = PTR_ERR(new_dentry);
> 4559 if (IS_ERR(new_dentry))
> goto exit4;
> 4561 error = -EEXIST;
> 4562 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
> goto exit5;
> 4564 if (flags & RENAME_EXCHANGE) {
> 4565 error = -ENOENT;
> 4566 if (d_is_negative(new_dentry))
> goto exit5;
>
> if (!d_is_dir(new_dentry)) {
> error = -ENOTDIR;
> 4571 if (new_last.name[new_last.len])
> goto exit5;
> }
> }
> /* unless the source is a directory trailing slashes give -ENOTDIR */
> if (!d_is_dir(old_dentry)) {
> 4577 error = -ENOTDIR;
> 4578 if (old_last.name[old_last.len])
> goto exit5;
> 4580 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
> goto exit5;
> }
> /* source should not be ancestor of target */
> 4584 error = -EINVAL;
> 4585 if (old_dentry == trap)
> goto exit5;
> /* target should not be an ancestor of source */
> if (!(flags & RENAME_EXCHANGE))
> 4589 error = -ENOTEMPTY;
> 4590 if (new_dentry == trap)
> goto exit5;
>
> error = security_path_rename(&old_path, old_dentry,
> &new_path, new_dentry, flags);
> if (error)
> goto exit5;
> 4597 error = vfs_rename(old_path.dentry->d_inode, old_dentry,
> new_path.dentry->d_inode, new_dentry,
> &delegated_inode, flags);
> exit5:
> 4601 dput(new_dentry);
> exit4:
> 4603 dput(old_dentry);
> exit3:
> 4605 unlock_rename(new_path.dentry, old_path.dentry);
> 4606 if (delegated_inode) {
> error = break_deleg_wait(&delegated_inode);
> 4608 if (!error)
> goto retry_deleg;
> }
> 4611 mnt_drop_write(old_path.mnt);
> exit2:
> if (retry_estale(error, lookup_flags))
> should_retry = true;
> path_put(&new_path);
> 4616 putname(to);
> exit1:
> path_put(&old_path);
> 4619 putname(from);
> 4620 if (should_retry) {
> should_retry = false;
> 4622 lookup_flags |= LOOKUP_REVAL;
> goto retry;
> }
> exit:
> return error;
> 4627 }
>
> 4629 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
> int, newdfd, const char __user *, newname, unsigned int, flags)
> {
> 4632 return do_renameat2(olddfd, oldname, newdfd, newname, flags);
> }
>
> 4635 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
> int, newdfd, const char __user *, newname)
> {
> 4638 return do_renameat2(olddfd, oldname, newdfd, newname, 0);
> }
>
> 4641 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
> {
> 4643 return do_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
> }
>
> int vfs_whiteout(struct inode *dir, struct dentry *dentry)
> 4647 {
> int error = may_create(dir, dentry);
> 4649 if (error)
> return error;
>
> 4652 if (!dir->i_op->mknod)
> 4653 return -EPERM;
>
> 4655 return dir->i_op->mknod(dir, dentry,
> S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
> 4657 }
> EXPORT_SYMBOL(vfs_whiteout);
>
> int readlink_copy(char __user *buffer, int buflen, const char *link)
> 4661 {
> 4662 int len = PTR_ERR(link);
> 4663 if (IS_ERR(link))
> goto out;
>
> 4666 len = strlen(link);
> if (len > (unsigned) buflen)
> len = buflen;
> 4669 if (copy_to_user(buffer, link, len))
> 4670 len = -EFAULT;
> out:
> return len;
> 4673 }
>
> /*
> * A helper for ->readlink(). This should be used *ONLY* for symlinks that
> * have ->get_link() not calling nd_jump_link(). Using (or not using) it
> * for any given inode is up to filesystem.
> */
> static int generic_readlink(struct dentry *dentry, char __user *buffer,
> int buflen)
> {
> 4683 DEFINE_DELAYED_CALL(done);
> struct inode *inode = d_inode(dentry);
> 4685 const char *link = inode->i_link;
> int res;
>
> 4688 if (!link) {
> 4689 link = inode->i_op->get_link(dentry, inode, &done);
> 4690 if (IS_ERR(link))
> 4691 return PTR_ERR(link);
> }
> 4693 res = readlink_copy(buffer, buflen, link);
> do_delayed_call(&done);
> return res;
> }
>
> /**
> * vfs_readlink - copy symlink body into userspace buffer
> * @dentry: dentry on which to get symbolic link
> * @buffer: user memory pointer
> * @buflen: size of buffer
> *
> * Does not touch atime. That's up to the caller if necessary
> *
> * Does not call security hook.
> */
> int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
> 4709 {
> 4710 struct inode *inode = d_inode(dentry);
>
> 4712 if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
> 4713 if (unlikely(inode->i_op->readlink))
> 4714 return inode->i_op->readlink(dentry, buffer, buflen);
>
> 4716 if (!d_is_symlink(dentry))
> 4717 return -EINVAL;
>
> spin_lock(&inode->i_lock);
> 4720 inode->i_opflags |= IOP_DEFAULT_READLINK;
> spin_unlock(&inode->i_lock);
> }
>
> return generic_readlink(dentry, buffer, buflen);
> 4725 }
> EXPORT_SYMBOL(vfs_readlink);
>
> /**
> * vfs_get_link - get symlink body
> * @dentry: dentry on which to get symbolic link
> * @done: caller needs to free returned data with this
> *
> * Calls security hook and i_op->get_link() on the supplied inode.
> *
> * It does not touch atime. That's up to the caller if necessary.
> *
> * Does not work on "special" symlinks like /proc/$$/fd/N
> */
> const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
> 4740 {
> const char *res = ERR_PTR(-EINVAL);
> 4742 struct inode *inode = d_inode(dentry);
>
> 4744 if (d_is_symlink(dentry)) {
> 4745 res = ERR_PTR(security_inode_readlink(dentry));
> 4746 if (!res)
> 4747 res = inode->i_op->get_link(dentry, inode, done);
> }
> return res;
> 4750 }
> EXPORT_SYMBOL(vfs_get_link);
>
> /* get the link contents into pagecache */
> const char *page_get_link(struct dentry *dentry, struct inode *inode,
> struct delayed_call *callback)
> 4756 {
> char *kaddr;
> struct page *page;
> 4759 struct address_space *mapping = inode->i_mapping;
>
> 4761 if (!dentry) {
> page = find_get_page(mapping, 0);
> 4763 if (!page)
> return ERR_PTR(-ECHILD);
> if (!PageUptodate(page)) {
> put_page(page);
> 4767 return ERR_PTR(-ECHILD);
> }
> } else {
> page = read_mapping_page(mapping, 0, NULL);
> 4771 if (IS_ERR(page))
> return (char*)page;
> }
> set_delayed_call(callback, page_put_link, page);
> 4775 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
> kaddr = page_address(page);
> nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
> return kaddr;
> 4779 }
>
> EXPORT_SYMBOL(page_get_link);
>
> void page_put_link(void *arg)
> 4784 {
> put_page(arg);
> 4786 }
> EXPORT_SYMBOL(page_put_link);
>
> int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
> 4790 {
> 4791 DEFINE_DELAYED_CALL(done);
> 4792 int res = readlink_copy(buffer, buflen,
> page_get_link(dentry, d_inode(dentry),
> &done));
> do_delayed_call(&done);
> return res;
> 4797 }
> EXPORT_SYMBOL(page_readlink);
>
> /*
> * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
> */
> int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
> 4804 {
> 4805 struct address_space *mapping = inode->i_mapping;
> struct page *page;
> void *fsdata;
> int err;
> 4809 unsigned int flags = 0;
> if (nofs)
> flags |= AOP_FLAG_NOFS;
>
> retry:
> 4814 err = pagecache_write_begin(NULL, mapping, 0, len-1,
> flags, &page, &fsdata);
> 4816 if (err)
> goto fail;
>
> 4819 memcpy(page_address(page), symname, len-1);
>
> 4821 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
> page, fsdata);
> 4823 if (err < 0)
> goto fail;
> 4825 if (err < len-1)
> goto retry;
>
> mark_inode_dirty(inode);
> 4829 return 0;
> fail:
> return err;
> 4832 }
> EXPORT_SYMBOL(__page_symlink);
>
> int page_symlink(struct inode *inode, const char *symname, int len)
> 4836 {
> 4837 return __page_symlink(inode, symname, len,
> !mapping_gfp_constraint(inode->i_mapping, __GFP_FS));
> }
> EXPORT_SYMBOL(page_symlink);

--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>

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