netdev - Re: [PATCH v2 net] tcp: take care of truncations done by sk

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Date:   Sun, 13 Nov 2016 12:30:27 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     vdronov@...hat.com, netdev@...r.kernel.org, marco.gra@...il.com
Subject: Re: [PATCH v2 net] tcp: take care of truncations done by
 sk_filter()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 10 Nov 2016 13:12:35 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> With syzkaller help, Marco Grassi found a bug in TCP stack,
> crashing in tcp_collapse()
> 
> Root cause is that sk_filter() can truncate the incoming skb,
> but TCP stack was not really expecting this to happen.
> It probably was expecting a simple DROP or ACCEPT behavior.
> 
> We first need to make sure no part of TCP header could be removed.
> Then we need to adjust TCP_SKB_CB(skb)->end_seq
> 
> Many thanks to syzkaller team and Marco for giving us a reproducer.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Marco Grassi <marco.gra@...il.com>
> Reported-by: Vladis Dronov <vdronov@...hat.com>
> ---
> v2: reload both th/iph in case skb->head changed.

Applied and queued up for -stable, thanks Eric.