linux-kernel - Re: use-after-free in sock_wake

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Message-ID: <1448483017.24696.33.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 25 Nov 2015 12:23:37 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Rainer Weikusat <rweikusat@...ileactivedefense.com>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Benjamin LaHaise <bcrl@...ck.org>,
	"David S. Miller" <davem@...emloft.net>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	David Howells <dhowells@...hat.com>,
	Ying Xue <ying.xue@...driver.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: use-after-free in sock_wake_async

On Wed, 2015-11-25 at 11:50 -0800, Eric Dumazet wrote:

> >                 other->sk_data_ready(other);
> > +               unix_state_unlock(other);


Also, problem with such construct is that we wakeup a thread that will
block on the lock we hold.

Beauty of sk_data_ready() is to call it once we hold no lock any more,
to enable another cpu to immediately proceed.

In this case, 'other' can not disappear, so it should be safe.


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