[ 3.5.y.z extended stable ] Patch "ipv6: ip6_sk_dst_check() must not assume ipv6 dst" has been added to staging queue

[Luis Henriques]

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

    ipv6: ip6_sk_dst_check() must not assume ipv6 dst

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.
-Luis

------

>From 806584e51b90af090eddb5d002ac855fd449be86 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Wed, 26 Jun 2013 04:15:07 -0700
Subject: [PATCH] ipv6: ip6_sk_dst_check() must not assume ipv6 dst

commit a963a37d384d71ad43b3e9e79d68d42fbe0901f3 upstream.

It's possible to use AF_INET6 sockets and to connect to an IPv4
destination. After this, socket dst cache is a pointer to a rtable,
not rt6_info.

ip6_sk_dst_check() should check the socket dst cache is IPv6, or else
various corruptions/crashes can happen.

Dave Jones can reproduce immediate crash with
trinity -q -l off -n -c sendmsg -c connect

With help from Hannes Frederic Sowa

Reported-by: Dave Jones <davej at redhat.com>
Reported-by: Hannes Frederic Sowa <hannes at stressinduktion.org>
Signed-off-by: Eric Dumazet <edumazet at google.com>
Acked-by: Hannes Frederic Sowa <hannes at stressinduktion.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/ipv6/ip6_output.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index ccb2adb..6c5f1c1 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -919,11 +919,17 @@ static struct dst_entry *ip6_sk_dst_check(struct sock *sk,
 					  const struct flowi6 *fl6)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
-	struct rt6_info *rt = (struct rt6_info *)dst;
+	struct rt6_info *rt;

 	if (!dst)
 		goto out;

+	if (dst->ops->family != AF_INET6) {
+		dst_release(dst);
+		return NULL;
+	}
+
+	rt = (struct rt6_info *)dst;
 	/* Yes, checking route validity in not connected
 	 * case is not very simple. Take into account,
 	 * that we do not support routing by source, TOS,
--
1.8.1.2