[CVE-2010-4342 Karmic] econet: Fix crash in aun_incoming(). CVE-2010-4342

[Leann Ogasawara]

The following changes since commit a03e8e64c82377c67d844a823e6a1ac673debc73:
  Tavis Ormandy (1):
        Revised [CVE-2010-4345 Karmic] install_special_mapping skips security_file_mmap check. CVE-2010-4346

are available in the git repository at:

  git://kernel.ubuntu.com/ogasawara/ubuntu-karmic.git CVE-2010-4342

David S. Miller (1):
      econet: Fix crash in aun_incoming(). CVE-2010-4342

 net/econet/af_econet.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

>From 9ed47256baebcd6389bfb10b9b40a5e6fc8a3bcf Mon Sep 17 00:00:00 2001
From: David S. Miller <davem at davemloft.net>
Date: Wed, 8 Dec 2010 18:42:23 -0800
Subject: [PATCH] econet: Fix crash in aun_incoming(). CVE-2010-4342

CVE-2010-4342

BugLink: http://bugs.launchpad.net/bugs/736394

Unconditional use of skb->dev won't work here,
try to fetch the econet device via skb_dst()->dev
instead.

Suggested by Eric Dumazet.

Reported-by: Nelson Elhage <nelhage at ksplice.com>
Tested-by: Nelson Elhage <nelhage at ksplice.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(backport of upstream commit 4e085e76cbe558b79b54cbab772f61185879bc64)

Signed-off-by: Leann Ogasawara <leann.ogasawara at canonical.com>
---
 net/econet/af_econet.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/net/econet/af_econet.c b/net/econet/af_econet.c
index 690da47..6bc2f6d 100644
--- a/net/econet/af_econet.c
+++ b/net/econet/af_econet.c
@@ -844,8 +844,12 @@ static void aun_incoming(struct sk_buff *skb, struct aunhdr *ah, size_t len)
 	struct iphdr *ip = ip_hdr(skb);
 	unsigned char stn = ntohl(ip->saddr) & 0xff;
 	struct sock *sk;
+	struct dst_entry *dst = skb_dst(skb);
+	struct ec_device *edev = NULL;
 	struct sk_buff *newskb;
-	struct ec_device *edev = skb->dev->ec_ptr;
+
+	if (dst)
+		edev = dst->dev->ec_ptr;
 
 	if (! edev)
 		goto bad;
-- 
1.7.0.4