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>

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 8133ca36ee0eaf320593afbf7e33d7c8c9e06a82..84ef378673a81708e4c11ed4dee4877fd9c1121f 100644 (file)
--- 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;