linux-kernel - Re: [RFC,PATCH 2/2] kill_pid_info: don't take now unneeded tasklist

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: <20080317170124.GA115@tv-sign.ru>
Date:	Mon, 17 Mar 2008 20:01:24 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Atsushi Tsuji <a-tsuji@...jp.nec.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Roland McGrath <roland@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Ingo Molnar <mingo@...e.hu>, Jiri Kosina <jkosina@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...nvz.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC,PATCH 2/2] kill_pid_info: don't take now unneeded tasklist_lock

On 03/17, Atsushi Tsuji wrote:
>
> (2008/03/05 3:57), Oleg Nesterov wrote:
> >Previously handle_stop_signal(SIGCONT) could drop ->siglock. That is why
> >kill_pid_info(SIGCONT) takes tasklist_lock to make sure the target task
> >can't go away after unlock. Not needed now.
> >
> >Signed-off-by: Oleg Nesterov <oleg@...sign.ru>
> 
> Hi Oleg,
> 
> I tried your patches on vanila kernel 2.6.25-rc3 (ia64).  Then, I got
> the NULL pointer dereference at task_session_nr(t) in
> check_kill_permission(). That is why t->signal->__session is accessed
> after t->signal was released.  It is reproducible by sending many
> SIGCONT signals to exiting processes.

Ah. Indeed!!! Thanks a lot Atsushi.

Note that check_kill_permission() is the last user of the deprecated
signal->__session/session, I was going to change this code later, but
missed the issue you pointed out.

I'll make the patch tomorrow.

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/