linux-kernel - [PATCH net] net: flow_dissector: fail on evil iph->ihl

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Date:	Fri,  1 Nov 2013 15:01:10 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	davem@...emloft.net, edumazet@...gle.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	Jason Wang <jasowang@...hat.com>,
	Petr Matousek <pmatouse@...hat.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Daniel Borkmann <dborkman@...hat.com>
Subject: [PATCH net] net: flow_dissector: fail on evil iph->ihl

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@...gle.com>
Cc: Petr Matousek <pmatouse@...hat.com>
Cc: Michael S. Tsirkin <mst@...hat.com>
Cc: Daniel Borkmann <dborkman@...hat.com>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
This patch is needed for stable.
---
 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 8d7d0dd..143b6fd 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -40,7 +40,7 @@ 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))
-- 
1.8.1.2

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