From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pavel Emelianov <xemul@sw.ru>
Subject: Re: [NETLINK] Don't attach callback to a going-away netlink socket
Date: Wed, 18 Apr 2007 12:32:40 +0400
Message-ID: <4625D7A8.5030209@sw.ru>
References: <4625D3D2.9030507@sw.ru> <20070418081707.GA29267@2ka.mipt.ru>
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Cc: David Miller <davem@davemloft.net>,
	Linux Netdev List <netdev@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	devel@openvz.org, Patrick McHardy <kaber@trash.net>,
	Kirill Korotaev <dev@openvz.org>
To: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Return-path: <linux-kernel-owner+glk-linux-kernel-3=40m.gmane.org-S933030AbXDRI1m@vger.kernel.org>
In-Reply-To: <20070418081707.GA29267@2ka.mipt.ru>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: netdev.vger.kernel.org

Evgeniy Polyakov wrote:
> On Wed, Apr 18, 2007 at 12:16:18PM +0400, Pavel Emelianov (xemul@sw.ru) wrote:
>> Sorry, I forgot to put netdev and David in Cc when I first sent it.
>>
>> There is a race between netlink_dump_start() and netlink_release()
>> that can lead to the situation when a netlink socket with non-zero
>> callback is freed.
> 
> Out of curiosity, why not to fix a netlink_dump_start() to remove
> callback in error path, since in 'no-error' path it removes it in

Error path is not relevant here. The problem is that we
keep a calback on a socket that is about to be freed.

> netlink_dump().
> 
> And, btw, can release method be called while socket is being used, I
> thought about proper reference counters should prevent this, but not
> 100% sure with RCU dereferencing of the descriptor.
>