linux-kernel - Re: [PATCH 2/2] posix-cpu-timers: use ->sighand instead of ->signal to check the task is alive

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] [day] [month] [year] [list]

Date:	Thu, 5 Feb 2009 23:59:44 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, Lin Ming <ming.m.lin@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] posix-cpu-timers: use ->sighand instead of
	->signal to check the task is alive

On 02/05, Roland McGrath wrote:
>
> > We can't use them as refcounts. You can't bump ->live or ->count without
> > breaking group_dead or exec logic. Perhaps we can use ->count, but then
> > we need other changes.
>
> We certainly need to clean up exec anyway.

Agreed.

> > The goal is to keep task->signal after release_task(), it will be freed
> > by __put_task_struct(). This allows a lot of simplifications and we can
> > move some fields from task_struct to signal_struct.
>
> That sounds fine to me in theory, but I still wonder what the story will be
> about the use of siglock.

I think we should change nothing with the usage of siglock for now?

> > But first we should change the code which does [...]
>
> I did understand the rationale given the signal_struct lifetime change.

Ah, sorry for noise then.

> > Even cpu_clock_sample_group() is not safe, unless we add other changes.
>
> Why?  It does no locking and only relies on the signal_struct lifetime.

Yes, I was wrong, thanks. I forgot we should always have a reference
to task_struct anyway.

Oleg.

--
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/