[3.5.y.z extended stable] Patch "net: flow_dissector: fail on evil iph->ihl" has been added to staging queue

[Luis Henriques]

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

    net: flow_dissector: fail on evil iph->ihl

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 8b68ad87a1f7f494e0b2e819ccd8d59a369ed5e8 Mon Sep 17 00:00:00 2001
From: Jason Wang <jasowang at redhat.com>
Date: Fri, 1 Nov 2013 15:01:10 +0800
Subject: net: flow_dissector: fail on evil iph->ihl

commit 6f092343855a71e03b8d209815d8c45bf3a27fcd upstream.

We don't validate iph->ihl which may lead a dead loop if we meet a IPIP
skb whose iph->ihl is zero. Fix this by failing immediately when iph->ihl
is evil (less than 5).

This issue were introduced by commit ec5efe7946280d1e84603389a1030ccec0a767ae
(rps: support IPIP encapsulation).

Cc: Eric Dumazet <edumazet at google.com>
Cc: Petr Matousek <pmatouse at redhat.com>
Cc: Michael S. Tsirkin <mst at redhat.com>
Cc: Daniel Borkmann <dborkman at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
Acked-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/core/flow_dissector.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 2774788..200707c 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -35,7 +35,7 @@ again:
 		struct iphdr _iph;
 ip:
 		iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
-		if (!iph)
+		if (!iph || iph->ihl < 5)
 			return false;

 		if (ip_is_fragment(iph))
--
1.8.3.2