netdev - [PATCH] netfilter: nf_conntrack_sip: don't drop packets with offsets pointing outside the packet

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Message-Id: <1365185610-2287-1-git-send-email-kaber@trash.net>
Date:	Fri,  5 Apr 2013 20:13:30 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	pablo@...filter.org
Cc:	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH] netfilter: nf_conntrack_sip: don't drop packets with offsets pointing outside the packet

Some Cisco phones create huge messages that are spread over multiple packets.
After calculating the offset of the SIP body, it is validated to be within
the packet and the packet is dropped otherwise. This breaks operation of
these phones. Since connection tracking is supposed to be passive, just let
those packets pass unmodified and untracked.

Signed-off-by: Patrick McHardy <kaber@...sh.net>
---
 net/netfilter/nf_conntrack_sip.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index 0e7d423..e0c4373 100644
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -1593,10 +1593,8 @@ static int sip_help_tcp(struct sk_buff *skb, unsigned int protoff,
 		end += strlen("\r\n\r\n") + clen;
 
 		msglen = origlen = end - dptr;
-		if (msglen > datalen) {
-			nf_ct_helper_log(skb, ct, "incomplete/bad SIP message");
-			return NF_DROP;
-		}
+		if (msglen > datalen)
+			return NF_ACCEPT;
 
 		ret = process_sip_msg(skb, ct, protoff, dataoff,
 				      &dptr, &msglen);
-- 
1.8.1.4

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