linux-kernel - Re: [PATCH 1/3] signals: fix sigqueue_free() vs __exit

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Date:	Tue, 20 May 2008 13:17:32 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Roland McGrath <roland@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] signals: fix sigqueue_free() vs __exit_signal() race

On 05/19, Andrew Morton wrote:
>
> On Sat, 17 May 2008 19:14:18 +0400 Oleg Nesterov <oleg@...sign.ru> wrote:
> 
> > __exit_signal() does flush_sigqueue(tsk->pending) outside of ->siglock.
> > This can race with another thread doing sigqueue_free(), we can free
> > the same SIGQUEUE_PREALLOC sigqueue twice or corrupt the pending->list.
> > 
> > Note that even sys_exit_group() can trigger this race, not only
> > sys_timer_delete().
> > 
> > Move the callsite of flush_sigqueue(tsk->pending) under ->siglock.
> > 
> > This patch doesn't touch flush_sigqueue(->shared_pending) below, it is
> > called when there are no other threads which can play with signals,
> > and sigqueue_free() can't be used outside of our thread group.
> 
> afacit this is the only needed-in-2.6.26 patch from these two
> three-patch series, yes?

Yes, other patches are not bugfixes.

Probably this fix is not "urgent" too, the race is very old and nobody
complained.

Oleg.

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