[PATCH 3/3] implement uid and gid mount options for ext4

From: Ludwig Nussel
Date: Fri May 11 2012 - 07:10:21 EST

Signed-off-by: Ludwig Nussel <ludwig.nussel@xxxxxxx>
---
Documentation/filesystems/ext4.txt | 9 ++++++
fs/ext4/ext4.h | 4 +++
fs/ext4/inode.c | 50 ++++++++++++++++++++++++++----------
fs/ext4/super.c | 49 ++++++++++++++++++++++++++++++++++-
4 files changed, 97 insertions(+), 15 deletions(-)

diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 1b7f9ac..b388ab5 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -245,6 +245,15 @@ resgid=n The group ID which may use the reserved blocks.

resuid=n The user ID which may use the reserved blocks.

+uid=n[:m] Make all files appear to belong to uid n.
+ Useful for e.g. removable media with fstab
+ options 'user,uid=useruid'. The optional second
+ uid m is actually written to the file system.
+
+gid=n[:m] Make all files appear to belong to gid n.
+ The optional second gid m is actually written to
+ the file system.
+
sb=n Use alternate superblock at this location.

quota These options are ignored by the filesystem. They
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0e01e90..7155b2d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1155,6 +1155,10 @@ struct ext4_sb_info {
ext4_fsblk_t s_sb_block;
uid_t s_resuid;
gid_t s_resgid;
+ uid_t s_uid; /* make all files appear to belong to this uid */
+ uid_t s_diskuid; /* write this uid to disk (if s_uid != 0) */
+ gid_t s_gid; /* make all files appear to belong to this gid */
+ gid_t s_diskgid; /* write this gid to disk (if s_gid != 0) */
unsigned short s_mount_state;
unsigned short s_pad;
int s_addr_per_block_bits;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c77b0bd..86ce928 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3651,6 +3651,10 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
inode->i_uid |= le16_to_cpu(raw_inode->i_uid_high) << 16;
inode->i_gid |= le16_to_cpu(raw_inode->i_gid_high) << 16;
}
+ if (EXT4_SB(sb)->s_uid)
+ inode->i_uid = EXT4_SB(sb)->s_uid;
+ if (EXT4_SB(sb)->s_gid)
+ inode->i_gid = EXT4_SB(sb)->s_gid;
set_nlink(inode, le16_to_cpu(raw_inode->i_links_count));

ext4_clear_state_flags(ei); /* Only relevant on 32-bit archs */
@@ -3868,8 +3872,14 @@ static int ext4_do_update_inode(handle_t *handle,
{
struct ext4_inode *raw_inode = ext4_raw_inode(iloc);
struct ext4_inode_info *ei = EXT4_I(inode);
+ uid_t uid = inode->i_uid;
+ gid_t gid = inode->i_gid;
struct buffer_head *bh = iloc->bh;
int err = 0, rc, block;
+ __le16 uid_low;
+ __le16 gid_low;
+ __le16 uid_high;
+ __le16 gid_high;

/* For fields not not tracking in the in-memory inode,
* initialise them to zero for new inodes. */
@@ -3878,30 +3888,42 @@ static int ext4_do_update_inode(handle_t *handle,

ext4_get_inode_flags(ei);
raw_inode->i_mode = cpu_to_le16(inode->i_mode);
+ if (EXT4_SB(inode->i_sb)->s_uid)
+ uid = EXT4_SB(inode->i_sb)->s_diskuid;
+ if (EXT4_SB(inode->i_sb)->s_gid)
+ gid = EXT4_SB(inode->i_sb)->s_diskgid;
if (!(test_opt(inode->i_sb, NO_UID32))) {
- raw_inode->i_uid_low = cpu_to_le16(low_16_bits(inode->i_uid));
- raw_inode->i_gid_low = cpu_to_le16(low_16_bits(inode->i_gid));
+ uid_low = cpu_to_le16(low_16_bits(uid));
+ gid_low = cpu_to_le16(low_16_bits(gid));
/*
* Fix up interoperability with old kernels. Otherwise, old inodes get
* re-used with the upper 16 bits of the uid/gid intact
*/
if (!ei->i_dtime) {
- raw_inode->i_uid_high =
- cpu_to_le16(high_16_bits(inode->i_uid));
- raw_inode->i_gid_high =
- cpu_to_le16(high_16_bits(inode->i_gid));
+ uid_high = cpu_to_le16(high_16_bits(uid));
+ gid_high = cpu_to_le16(high_16_bits(gid));
} else {
- raw_inode->i_uid_high = 0;
- raw_inode->i_gid_high = 0;
+ uid_high = 0;
+ gid_high = 0;
}
} else {
- raw_inode->i_uid_low =
- cpu_to_le16(fs_high2lowuid(inode->i_uid));
- raw_inode->i_gid_low =
- cpu_to_le16(fs_high2lowgid(inode->i_gid));
- raw_inode->i_uid_high = 0;
- raw_inode->i_gid_high = 0;
+ uid_low = cpu_to_le16(fs_high2lowuid(uid));
+ gid_low = cpu_to_le16(fs_high2lowgid(gid));
+ uid_high = 0;
+ gid_high = 0;
}
+ /* don't mangle uid/gid of existing files if override is active */
+ if (!EXT4_SB(inode->i_sb)->s_uid ||
+ ext4_test_inode_state(inode, EXT4_STATE_NEW)) {
+ raw_inode->i_uid_high = uid_high;
+ raw_inode->i_uid_low = uid_low;
+ }
+ if (!EXT4_SB(inode->i_sb)->s_gid ||
+ ext4_test_inode_state(inode, EXT4_STATE_NEW)) {
+ raw_inode->i_gid_high = gid_high;
+ raw_inode->i_gid_low = gid_low;
+ }
+
raw_inode->i_links_count = cpu_to_le16(inode->i_nlink);

EXT4_INODE_SET_XTIME(i_ctime, inode, raw_inode);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e1fb1d5..5f121f3 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1186,6 +1186,7 @@ enum {
Opt_inode_readahead_blks, Opt_journal_ioprio,
Opt_dioread_nolock, Opt_dioread_lock,
Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
+ Opt_uid, Opt_diskuid, Opt_gid, Opt_diskgid,
};

static const match_table_t tokens = {
@@ -1264,6 +1265,10 @@ static const match_table_t tokens = {
{Opt_removed, "reservation"}, /* mount option from ext2/3 */
{Opt_removed, "noreservation"}, /* mount option from ext2/3 */
{Opt_removed, "journal=%u"}, /* mount option from ext2/3 */
+ {Opt_uid, "uid=%u"},
+ {Opt_diskuid, "uid=%u:%u"},
+ {Opt_gid, "gid=%u"},
+ {Opt_diskgid, "gid=%u:%u"},
{Opt_err, NULL},
};

@@ -1498,6 +1503,24 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
return -1;
*journal_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, arg);
return 1;
+ case Opt_uid:
+ sbi->s_uid = sbi->s_diskuid = arg;
+ return 1;
+ case Opt_diskuid:
+ sbi->s_uid = arg;
+ if (match_int(&args[1], &arg))
+ return -1;
+ sbi->s_diskuid = arg;
+ return 1;
+ case Opt_gid:
+ sbi->s_gid = sbi->s_diskgid = arg;
+ return 1;
+ case Opt_diskgid:
+ sbi->s_gid = arg;
+ if (match_int(&args[1], &arg))
+ return -1;
+ sbi->s_diskgid = arg;
+ return 1;
}

for (m = ext4_mount_opts; m->token != Opt_err; m++) {
@@ -1713,7 +1736,7 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
char sep = nodefs ? '\n' : ',';

#define SEQ_OPTS_PUTS(str) seq_printf(seq, "%c" str, sep)
-#define SEQ_OPTS_PRINT(str, arg) seq_printf(seq, "%c" str, sep, arg)
+#define SEQ_OPTS_PRINT(str, args...) seq_printf(seq, "%c" str, sep, ##args)

if (sbi->s_sb_block != 1)
SEQ_OPTS_PRINT("sb=%llu", sbi->s_sb_block);
@@ -1738,6 +1761,18 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
if (nodefs || sbi->s_resgid != EXT4_DEF_RESGID ||
le16_to_cpu(es->s_def_resgid) != EXT4_DEF_RESGID)
SEQ_OPTS_PRINT("resgid=%u", sbi->s_resgid);
+ if (sbi->s_uid) {
+ if (sbi->s_uid != sbi->s_diskuid)
+ SEQ_OPTS_PRINT("uid=%u:%u", sbi->s_uid, sbi->s_diskuid);
+ else
+ SEQ_OPTS_PRINT("uid=%u", sbi->s_uid);
+ }
+ if (sbi->s_gid) {
+ if (sbi->s_gid != sbi->s_diskgid)
+ SEQ_OPTS_PRINT("gid=%u:%u", sbi->s_gid, sbi->s_diskgid);
+ else
+ SEQ_OPTS_PRINT("gid=%u", sbi->s_gid);
+ }
def_errors = nodefs ? -1 : le16_to_cpu(es->s_errors);
if (test_opt(sb, ERRORS_RO) && def_errors != EXT4_ERRORS_RO)
SEQ_OPTS_PUTS("errors=remount-ro");
@@ -4215,6 +4250,10 @@ struct ext4_mount_options {
unsigned long s_mount_opt2;
uid_t s_resuid;
gid_t s_resgid;
+ uid_t s_uid;
+ uid_t s_diskuid;
+ gid_t s_gid;
+ gid_t s_diskgid;
unsigned long s_commit_interval;
u32 s_min_batch_time, s_max_batch_time;
#ifdef CONFIG_QUOTA
@@ -4245,6 +4284,10 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
old_opts.s_mount_opt2 = sbi->s_mount_opt2;
old_opts.s_resuid = sbi->s_resuid;
old_opts.s_resgid = sbi->s_resgid;
+ old_opts.s_uid = sbi->s_uid;
+ old_opts.s_diskuid = sbi->s_diskuid;
+ old_opts.s_gid = sbi->s_gid;
+ old_opts.s_diskgid = sbi->s_diskgid;
old_opts.s_commit_interval = sbi->s_commit_interval;
old_opts.s_min_batch_time = sbi->s_min_batch_time;
old_opts.s_max_batch_time = sbi->s_max_batch_time;
@@ -4402,6 +4445,10 @@ restore_opts:
sbi->s_mount_opt2 = old_opts.s_mount_opt2;
sbi->s_resuid = old_opts.s_resuid;
sbi->s_resgid = old_opts.s_resgid;
+ sbi->s_uid = old_opts.s_uid;
+ sbi->s_diskuid = old_opts.s_diskuid;
+ sbi->s_gid = old_opts.s_gid;
+ sbi->s_diskgid = old_opts.s_diskgid;
sbi->s_commit_interval = old_opts.s_commit_interval;
sbi->s_min_batch_time = old_opts.s_min_batch_time;
sbi->s_max_batch_time = old_opts.s_max_batch_time;
--
1.7.7

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