linux-kernel - Re: [PATCH] net: af_unix: protect ->sk_shutdown change with lock

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Message-ID: <a070f6f7-ed85-c909-ce8b-748210402211@stressinduktion.org>
Date:	Wed, 18 May 2016 12:38:36 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	"David S. Miller" <davem@...emloft.net>
Cc:	Rainer Weikusat <rweikusat@...ileactivedefense.com>,
	Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: af_unix: protect ->sk_shutdown change with
 lock_sock()

On 18.05.2016 12:14, Andrey Ryabinin wrote:
> ->sk_shutdown bits share one bitfield with some other bits in sock struct,
> such as ->sk_no_check_[r,t]x, ->sk_userlocks ...
> sock_setsockopt() may write to these bits, while holding the socket lock.
> In case of AF_UNIX sockets, we change ->sk_shutdown bits while holding only
> unix_state_lock(). So concurrent setsockopt() and shutdown() may lead
> to corrupting these bits.
> 
> Fix that by protecting writes to ->sk_shutdown with lock_sock()

Is it possible to move sk_shutdown out of the bitfields? Maybe a whole
which suites is available somewhere?

af_unix doesn't depend on the socket locks anywhere and it would keep
locking much easier if we only depend on the state lock.

Bye,
Hannes