sysfs: fix i_mutex locking in sysfs_get_dentry()

lookup_one_len_kern() should be called with the parent's i_mutex
locked.  Fix it.

Spotted by Eric W. Biederman.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index a0da2b05a754..54ca4bc02dcf 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -130,8 +130,10 @@ struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd)
 
                 /* look it up */
                 parent_dentry = dentry;
+                mutex_lock(&parent_dentry->d_inode->i_mutex);
                 dentry = lookup_one_len_kern(cur->s_name, parent_dentry,
                                              strlen(cur->s_name));
+                mutex_unlock(&parent_dentry->d_inode->i_mutex);
                 dput(parent_dentry);
 
                 if (IS_ERR(dentry)) {