[PATCH 3/3] sysfs: Take sysfs_mutex when fetching the root inode.

[Eric W. Biederman]

sysfs_get_inode ultimately calls sysfs_count_nlink when the a
directory inode is fectched.  sysfs_count_nlink needs to be called
under the sysfs_mutex to guard against the unlikely but possible
scenario that the root directory is changing as we are counting the
number entries in it.

Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
---
 fs/sysfs/mount.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 8f2237a..59e55f0 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -65,7 +65,9 @@ static int sysfs_fill_super(struct super_block *sb, void *data, int silent,
 
 	/* get root inode, initialize and unlock it */
 	error = -ENOMEM;
+	mutex_lock(&sysfs_mutex);
 	inode = sysfs_get_inode(&sysfs_root);
+	mutex_unlock(&sysfs_mutex);
 	if (!inode) {
 		pr_debug("sysfs: could not get root inode\n");
 		goto out_err;
-- 
1.5.3.rc6.17.g1911

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