From: Pavel Shilovsky <piastryyy@gmail.com>
Date: Mon, 25 Jul 2011 13:59:10 +0000 (+0400)
Subject: CIFS: Fix oops while mounting with prefixpath
X-Git-Tag: next-20110726~95^2~9
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=3ca30d40a91fb9b9871e61d5dea2c1a895906a15;p=karo-tx-linux.git

CIFS: Fix oops while mounting with prefixpath

commit fec11dd9a0109fe52fd631e5c510778d6cbff6cc caused
a regression when we have already mounted //server/share/a
and want to mount //server/share/a/b.

The problem is that lookup_one_len calls __lookup_hash
with nd pointer as NULL. Then __lookup_hash calls
do_revalidate in the case when dentry exists and we end
up with NULL pointer deference in cifs_d_revalidate:

if (nd->flags & LOOKUP_RCU)
	return -ECHILD;

Fix this by checking nd for NULL.

Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 14d602f178c2..499f27fc8576 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -641,7 +641,7 @@ lookup_out:
 static int
 cifs_d_revalidate(struct dentry *direntry, struct nameidata *nd)
 {
-	if (nd->flags & LOOKUP_RCU)
+	if (nd && (nd->flags & LOOKUP_RCU))
 		return -ECHILD;
 
 	if (direntry->d_inode) {