linux-kernel - Re: [PATCH] ftrace: do_each_pid

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:	Wed, 4 Feb 2009 01:12:43 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <srostedt@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: do_each_pid_task() needs rcu lock

On 02/03, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg@...hat.com> writes:
>
> > Yes, I thought about de_thread() too. But we can't "fix" do_each_pid_task()
> > to avoid the race?
>
> For the case of exec there is that.  There is also the case that
> ftrace unlike everything else wants to trace be able to trace all of
> the idle threads with pid 0.  I think that is a special case
> currently, but for that case the only correct version I can think
> of do_each_task_pid(), and current do_each_task_pid is wrong because
> it does not allow that.

Well, yes, I (partly) agree.

But, if we are talking about idle threads, we should change copy_process()
first. Because fork_idle()->copy_process(..., pid => init_struct_pid, ...)
means we don't really attach the idle thread to init_struct_pid.

I must admit, I think we should keep init_struct_pid "special" anyway,
but in any case you are right imho, there are nasty oddities here.

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/