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xt_qtaguid: Fix panic caused by synack processing

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In upstream commit ca6fb06518
(tcp: attach SYNACK messages to request sockets instead of
listener)
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ca6fb0651883

The building of synack messages was changed, which made it so
the skb->sk points to a casted request_sock. This is problematic,
as there is no sk_socket in a request_sock. So when the qtaguid_mt
function tries to access the sk->sk_socket, it accesses uninitialized
memory.

After looking at how other netfilter implementations handle this,
I realized there was a skb_to_full_sk() helper added, which the
xt_qtaguid code isn't yet using.

This patch adds its use, and resovles panics seen when accessing
uninitialzed memory when processing synack packets.

Reported-by: YongQin Liu <yongquin.liu@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
This commit is contained in:
John Stultz 2016-04-22 17:12:57 -07:00 • committed by Amit Pundir
parent 52a20402ae
commit 202d12a1f7
1 changed files with 1 additions and 1 deletions
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2
net/netfilter/xt_qtaguid.c
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@ -1689,7 +1689,7 @@ static bool qtaguid_mt(const struct sk_buff *skb, struct xt_action_param *par)
/* default: Fall through and do UID releated work */
}
sk = skb->sk;
sk = skb_to_full_sk(skb);
/*
* When in TCP_TIME_WAIT the sk is not a "struct sock" but
* "struct inet_timewait_sock" which is missing fields.