linux-kernel - Re: [PATCH 2/9] perf_counter: fix update

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1238664517.8530.5705.camel@twins>
Date:	Thu, 02 Apr 2009 11:28:37 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Paul Mackerras <paulus@...ba.org>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Wu Fengguang <fengguang.wu@...el.com>
Subject: Re: [PATCH 2/9] perf_counter: fix update_userpage()

On Thu, 2009-04-02 at 20:21 +1100, Paul Mackerras wrote:
> Peter Zijlstra writes:
> 
> > The below might work:
> > 
> >   u32 seq;
> >   s64 count;
> > 
> > again:
> >   seq = pc->lock;
> > 
> >   if (unlikely(seq & 1)) {
> 
> I don't believe we can ever see this condition, since pc->lock is
> updated in the kernel either at interrupt level on the cpu this task
> is running on, or in the kernel in the context of this task.  So this
> userspace code can never run in the middle of the kernel updating
> things.

Colour me paranoid ;-)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/