sysfs: Take sysfs_mutex when fetching the root inode.

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, and just in
general to be consistent.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 8133ca36ee0..84ef378673a 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -52,7 +52,9 @@ static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
         sysfs_sb = sb;
 
         /* get root inode, initialize and unlock it */
+        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");
                 return -ENOMEM;