netdev - Re: [PATCH net] pptp: fix illegal memory access caused by multiple bind()s

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Date:	Sun, 24 Jan 2016 22:18:59 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	hannes@...essinduktion.org
Cc:	netdev@...r.kernel.org, xeb@...l.ru, sasha.levin@...cle.com,
	dvyukov@...gle.com, davej@...emonkey.org.uk
Subject: Re: [PATCH net] pptp: fix illegal memory access caused by multiple
 bind()s

From: Hannes Frederic Sowa <hannes@...essinduktion.org>
Date: Fri, 22 Jan 2016 01:39:43 +0100

> Several times already this has been reported as kasan reports caused by
> syzkaller and trinity and people always looked at RCU races, but it is
> much more simple. :)
> 
> In case we bind a pptp socket multiple times, we simply add it to
> the callid_sock list but don't remove the old binding. Thus the old
> socket stays in the bucket with unused call_id indexes and doesn't get
> cleaned up. This causes various forms of kasan reports which were hard
> to pinpoint.
> 
> Simply don't allow multiple binds and correct error handling in
> pptp_bind. Also keep sk_state bits in place in pptp_connect.
> 
> Fixes: 00959ade36acad ("PPTP: PPP over IPv4 (Point-to-Point Tunneling Protocol)")
> Cc: Dmitry Kozlov <xeb@...l.ru>
> Cc: Sasha Levin <sasha.levin@...cle.com>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Dave Jones <davej@...emonkey.org.uk>
> Reported-by: Dave Jones <davej@...emonkey.org.uk>
> Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Applied and queued up for -stable, thanks Hannes.