[PATCH 06/15] Introduce sysfs_sd_setattr and fix sysfs_chmod

[Eric W. Biederman]

Currently sysfs_chmod calls sys_setattr which in turn calls
inode_change_ok which checks to see if it is ok for the current user
space process to change tha attributes. Since sysfs_chmod_file has
only kernel mode clients denying them permission if user space is the
problem is completely inappropriate.

Therefore factor out sysfs_sd_setattr which does not call
inode_change_ok and modify sysfs_chmod_file to call it.

In addition setting victim_sd->s_mode explicitly in sysfs_chmod_file
is redundant so remove that as well.

Thanks to Tejun Heo <htejun@xxxxxxxxx>, and
Daniel Lezcano <dlezcano@xxxxxxxxxx> for working on this
and spotting this case.

Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
---
 fs/sysfs/file.c  |    5 +----
 fs/sysfs/inode.c |   23 ++++++++++++++++-------
 fs/sysfs/sysfs.h |    1 +
 3 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index cb5dd3f..1304b3a 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -600,13 +600,10 @@ int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
 	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 	newattrs.ia_ctime = current_fs_time(inode->i_sb);
-	rc = sysfs_setattr(victim, &newattrs);
+	rc = sysfs_sd_setattr(victim_sd, inode, &newattrs);
 
 	if (rc == 0) {
 		fsnotify_change(victim, newattrs.ia_valid);
-		mutex_lock(&sysfs_mutex);
-		victim_sd->s_mode = newattrs.ia_mode;
-		mutex_unlock(&sysfs_mutex);
 	}
 
 	mutex_unlock(&inode->i_mutex);
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index eb53c63..80f8fd4 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -42,10 +42,9 @@ int __init sysfs_inode_init(void)
 	return bdi_init(&sysfs_backing_dev_info);
 }
 
-int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
+int sysfs_sd_setattr(struct sysfs_dirent *sd, struct inode *inode,
+			struct iattr * iattr)
 {
-	struct inode * inode = dentry->d_inode;
-	struct sysfs_dirent * sd = dentry->d_fsdata;
 	struct iattr * sd_iattr;
 	unsigned int ia_valid = iattr->ia_valid;
 	int error;
@@ -55,10 +54,6 @@ int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
 
 	sd_iattr = sd->s_iattr;
 
-	error = inode_change_ok(inode, iattr);
-	if (error)
-		return error;
-
 	iattr->ia_valid &= ~ATTR_SIZE; /* ignore size changes */
 
 	error = inode_setattr(inode, iattr);
@@ -104,6 +99,20 @@ int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
 	return error;
 }
 
+int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
+{
+	struct inode * inode = dentry->d_inode;
+	struct sysfs_dirent * sd = dentry->d_fsdata;
+	int error;
+
+	error = inode_change_ok(inode, iattr);
+	if (error)
+		return error;
+
+	return sysfs_sd_setattr(sd, inode, iattr);
+}
+
+
 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
 {
 	inode->i_mode = mode;
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index b1bdc6e..5ee5d0a 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -154,6 +154,7 @@ static inline void sysfs_put(struct sysfs_dirent *sd)
  * inode.c
  */
 struct inode *sysfs_get_inode(struct sysfs_dirent *sd);
+int sysfs_sd_setattr(struct sysfs_dirent *sd, struct inode *inode, struct iattr *iattr);
 int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
 int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name);
 int sysfs_inode_init(void);
-- 
1.5.3.rc6.17.g1911

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