linux-kernel - [026/102] CIFS: Fix oops while mounting with prefixpath

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Message-Id: <20110803221246.626130921@clark.kroah.org>
Date:	Wed, 03 Aug 2011 15:00:46 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Pavel Shilovsky <piastryyy@...il.com>,
	Steve French <sfrench@...ibm.com>
Subject: [026/102] CIFS: Fix oops while mounting with prefixpath

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Pavel Shilovsky <piastryyy@...il.com>

commit f5bc1e755d23d022bf948904386337fc3e5e29a8 upstream.

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@...il.com>
Reviewed-by: Shirish Pargaonkar <shirishp@...ibm.com>
Signed-off-by: Steve French <sfrench@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/cifs/dir.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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) {


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