From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1755380AbdCPQn3 (ORCPT <rfc822;w@1wt.eu>);
        Thu, 16 Mar 2017 12:43:29 -0400
Received: from mx1.redhat.com ([209.132.183.28]:36376 "EHLO mx1.redhat.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1752438AbdCPQn1 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 16 Mar 2017 12:43:27 -0400
DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com BADB1437F76
Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com
Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=oleg@redhat.com
DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com BADB1437F76
Date: Thu, 16 Mar 2017 17:41:24 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        syzkaller <syzkaller@googlegroups.com>
Subject: Re: perf: use-after-free in perf_release
Message-ID: <20170316164124.GA29048@redhat.com>
References: <20170314125508.GK3343@twins.programming.kicks-ass.net> <20170314140302.GA28146@redhat.com> <20170314140754.GG3328@twins.programming.kicks-ass.net> <20170314143010.GA30351@redhat.com> <20170314150241.GO5680@worktop> <20170314151910.GA31766@redhat.com> <20170314152625.GP5680@worktop> <20170314155949.GE32474@worktop> <20170315164302.GA17317@redhat.com> <20170316135735.5psknfxe7e73gnag@hirez.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170316135735.5psknfxe7e73gnag@hirez.programming.kicks-ass.net>
User-Agent: Mutt/1.5.18 (2008-05-17)
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 16 Mar 2017 16:43:23 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 03/16, Peter Zijlstra wrote:
>
> On Wed, Mar 15, 2017 at 05:43:02PM +0100, Oleg Nesterov wrote:
> > 	static inline int list_is_first(const struct list_head *list,
> > 					const struct list_head *head)
> > 	{
> > 		return head->next == list;
> > 	}
> >
> > won't be symmetrical with list_is_last() we already have.
>
> This is the one that makes sense to me though; that is, the current
> list_is_last() doesn't make sense to me.
>
> I would expect:
>
> static inline int list_is_last(const struct list_head *list,
> 				const struct list_head *head)
> {
> 	return head->prev == list
> }

Yes!

> because @head is the list argument (yes, I know, horrible naming!).

and perhaps it could have more users if we redefine it to dereference
"head" which is likely more "stable", iow less likely can go away.

But after the quick grep I came to conclusion it is not possible to
audit the users it already has.

Oleg.