sysfs: make sysfs_lookup() return ERR_PTR(-ENOENT) on failed lookup

sysfs tries to keep dcache a strict subset of sysfs_dirent tree by
shooting down dentries when a node is removed, that is, no negative
dentry for sysfs.  However, the lookup function returned NULL and thus
created negative dentries when the target node didn't exist.

Make sysfs_lookup() return ERR_PTR(-ENOENT) on lookup failure.  This
fixes the NULL dereference bug in sysfs_get_dentry() discovered by
bluetooth rfcomm device moving around.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 337162935d21..b197016bbfbe 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -678,8 +678,10 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
         sd = sysfs_find_dirent(parent_sd, dentry->d_name.name);
 
         /* no such entry */
-        if (!sd)
+        if (!sd) {
+                ret = ERR_PTR(-ENOENT);
                 goto out_unlock;
+        }
 
         /* attach dentry and inode */
         inode = sysfs_get_inode(sd);