From: Patrick McHardy <kaber@trash.net>
Date: Mon, 30 Sep 2013 07:51:46 +0000 (+0100)
Subject: netfilter: synproxy: fix BUG_ON triggered by corrupt TCP packets
X-Git-Tag: v3.12-rc4~30^2~4^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f4a87e7bd2eaef26a3ca25437ce8b807de2966ad;p=pandora-kernel.git

netfilter: synproxy: fix BUG_ON triggered by corrupt TCP packets

TCP packets hitting the SYN proxy through the SYNPROXY target are not
validated by TCP conntrack. When th->doff is below 5, an underflow happens
when calculating the options length, causing skb_header_pointer() to
return NULL and triggering the BUG_ON().

Handle this case gracefully by checking for NULL instead of using BUG_ON().

Reported-by: Martin Topholm <mph@one.com>
Tested-by: Martin Topholm <mph@one.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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