linux-kernel - Re: [PATCH] pidns: reboot_pid_ns: use SEND_SIG_FORCED instead of force

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: <20120417183513.GA1037@redhat.com>
Date:	Tue, 17 Apr 2012 20:35:13 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Serge Hallyn <serge.hallyn@...onical.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Lezcano <daniel.lezcano@...e.fr>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pidns: reboot_pid_ns: use SEND_SIG_FORCED instead of
	force_sig()

On 04/16, Oleg Nesterov wrote:
>
> I'll investigate and report tomorrow.

Thanks again Serge, everything is clear. Afaics this needs another
(almost off-topic) patch.

Please forget about sys_reboot() for the moment. There is a minor
and known problem with SIGKILL && SIGNAL_UNKILLABLE. If you send
SIGKILL from the parent namespace to cinit, this doesn't make it
SIGNAL_GROUP_EXIT immediately. Only after cinit actually dequeues
SIGKILL it does do_group_exit() and set this flag. This should be
fixed anyway, but not now.

And this explain the problem. Note that your test-case does
sys_reboot() from the init process, and reboot_pid_ns() does

	kill(pid_ns->child_reaper, SIGKILL);

	do_exit(0);

so it sends SIGKILL to itself and exit. This means that cinit
(current) obviously can't dequeue SIGKILL, and without
SIGNAL_GROUP_EXIT wait_task_zombie() ignores
signal->group_exit_code.

That is why the patch makes a difference.

But why reboot_pid_ns() does do_exit? Yes, it was copied from
sys_reboot() and I didn't notice. It should use do_group_exit(),
and sys_reboot() too. This is the patch I am going to send, but
I'll try to think a bit more.

Thanks!

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/