linux-kernel - Re: Deadlock between bind and splice

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Message-ID: <20151110025906.GA22011@ZenIV.linux.org.uk>
Date:	Tue, 10 Nov 2015 02:59:06 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Dmitry Vyukov <dvyukov@...gle.com>, linux-fsdevel@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	syzkaller <syzkaller@...glegroups.com>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>
Subject: Re: Deadlock between bind and splice

On Tue, Nov 10, 2015 at 02:38:54AM +0000, Al Viro wrote:
> On Fri, Nov 06, 2015 at 07:42:15AM -0800, Eric Dumazet wrote:
> 
> > Thank you for this report.
> > 
> > pipe is part of fs, not net ;)
> 
> AF_UNIX bind() vs. socketpair() interplay, OTOH...

FWIW, BSD folks unlock the socket for the duration of mknod - mark it as
"somebody's trying to bind it" to avoid the fun with racing double bind(),
but that's about it.  Tempting, to be honest...

BTW, why does unix_autobind() do allocation under ->readlock?  The allocation
will be normally used - that if (u->addr) return; part is just dealing with
an unlikely race, as far as I can see...
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