linux-kernel - Re: net/unix: sk_socket can disappear when state is unlocked

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Message-ID: <555F583B.1010309@android.com>
Date:	Fri, 22 May 2015 09:24:27 -0700
From:	Mark Salyzyn <salyzyn@...roid.com>
To:	Hannes Frederic Sowa <hannes@...hat.com>
CC:	linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	David Howells <dhowells@...hat.com>,
	Ying Xue <ying.xue@...driver.com>,
	Christoph Hellwig <hch@....de>, netdev@...r.kernel.org
Subject: Re: net/unix: sk_socket can disappear when state is unlocked

On 05/22/2015 08:35 AM, Hannes Frederic Sowa wrote:
> I still wonder if we need to actually recheck the condition and not
> simply break out of unix_stream_data_wait:
>
> We return to the unix_stream_recvmsg loop and recheck the
> sk_receive_queue. At this point sk_receive_queue is not really protected
> with unix_state_lock against concurrent modification with unix_release,
> as such we could end up concurrently dequeueing packets if socket is
> DEAD.
sock destroy(sic) is called before sock_orphan which sets SOCK_DEAD, so 
the receive queue has already been drained.

Sincerely -- Mark Salyzyn
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