netdev - Re: use-after-free in sock_wake

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Message-ID: <1448489350.24696.47.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 25 Nov 2015 14:09:10 -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 20:57 +0000, Rainer Weikusat wrote:

> I do agree that keeping the ->sk_data_ready outside of the lock will
> very likely have performance advantages. That's just something I
> wouldn't have undertaken because I'd be reluctant to make a fairly
> complicated change to a lot of code.

All I am saying is that we can keep current performance.

We already have the core infrastructure, we only need to properly use
it.

I will split my changes in two parts.

One part doing a very boring change of

rename SOCK_ASYNC_NOSPACE and SOCK_ASYNC_WAITDATA
for X in SOCK_ASYNC_NOSPACE SOCK_ASYNC_WAITDATA 

 set_bit(X, &sk->sk_socket->flags) -> sk_set_bit(X, sk)
 clear_bit(X, &sk->sk_socket->flags) -> sk_clear_bit(X, sk)

The rename will help backports to catch code that might have been
removed in recent kernels.

Then the second patch will do the actual changes, and they will look
very sensible for people wanting to review them, and or familiar with
the stack, do not worry ;)



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