[ 3.5.y.z extended stable ] Patch "NFS: avoid NULL dereference in nfs_destroy_server" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    NFS: avoid NULL dereference in nfs_destroy_server

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From 3cd610a5f45330272e6f0972bab7111367b42dc1 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb at suse.de>
Date: Thu, 13 Dec 2012 15:14:36 +1100
Subject: [PATCH] NFS: avoid NULL dereference in nfs_destroy_server

commit f259613a1e4b44a0cf85a5dafd931be96ee7c9e5 upstream.

In rare circumstances, nfs_clone_server() of a v2 or v3 server can get
an error between setting server->destory (to nfs_destroy_server), and
calling nfs_start_lockd (which will set server->nlm_host).

If this happens, nfs_clone_server will call nfs_free_server which
will call nfs_destroy_server and thence nlmclnt_done(NULL).  This
causes the NULL to be dereferenced.

So add a guard to only call nlmclnt_done() if ->nlm_host is not NULL.

The other guards there are irrelevant as nlm_host can only be non-NULL
if one of these flags are set - so remove those tests.  (Thanks to Trond
for this suggestion).

This is suitable for any stable kernel since 2.6.25.

Signed-off-by: NeilBrown <neilb at suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust at netapp.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 fs/nfs/client.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index f005b5b..ede78be 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -689,8 +689,7 @@ static int nfs_create_rpc_client(struct nfs_client *clp,
  */
 static void nfs_destroy_server(struct nfs_server *server)
 {
-	if (!(server->flags & NFS_MOUNT_LOCAL_FLOCK) ||
-			!(server->flags & NFS_MOUNT_LOCAL_FCNTL))
+	if (server->nlm_host)
 		nlmclnt_done(server->nlm_host);
 }

--
1.7.9.5