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From: Jason Wang <jasowang@redhat.com>
Newsgroups: gmane.linux.kernel,gmane.linux.network
Subject: [PATCH net] net: flow_dissector: fail on evil iph->ihl
Date: Fri,  1 Nov 2013 15:01:10 +0800
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Cc: Jason Wang <jasowang@redhat.com>,
	Petr Matousek <pmatouse@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Daniel Borkmann <dborkman@redhat.com>
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Xref: news.gmane.org gmane.linux.kernel:1588387 gmane.linux.network:289242
Archived-At: <http://permalink.gmane.org/gmane.linux.kernel/1588387>
 
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@google.com>
Cc: Petr Matousek <pmatouse@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.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