linux-kernel - Re: [PATCH] fix group stop with exit race

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]

Date:	Wed, 5 Dec 2007 17:08:47 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Oleg Nesterov <oleg@...sign.ru>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Roland McGrath <roland@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fix group stop with exit race

On Wed, 5 Dec 2007, Oleg Nesterov wrote:

> do_signal_stop() counts all sub-thread and sets ->group_stop_count accordingly.
> Every thread should decrement ->group_stop_count and stop, the last one should
> notify the parent.
> 
> However a sub-thread can exit before it notices the signal_pending(), or it may
> be somewhere in do_exit() already. In that case the group stop never finishes
> properly.
> 
> Note: this is a minimal fix, we can add some optimizations later. Say we can
> return quickly if thread_group_empty(). Also, we can move some signal related
> code from exit_notify() to exit_signals().
> 
> Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

Looks OK for me, even though we're doing more work on the exit path. OTOH 
I don't see a non-racy way of doing it w/out grabbing the lock. Did you 
try to bench how much this change costs?
Anyway, looks sane to me...

Acked-by: Davide Libenzi <davidel@...ilserver.org>



- Davide


--
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/