From: Oleg Nesterov <oleg@tv-sign.ru>
To: Atsushi Tsuji <a-tsuji@bk.jp.nec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Roland McGrath <roland@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Davide Libenzi <davidel@xmailserver.org>,
Ingo Molnar <mingo@elte.hu>, Jiri Kosina <jkosina@suse.cz>,
Linus Torvalds <torvalds@linux-foundation.org>,
Pavel Emelyanov <xemul@openvz.org>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC,PATCH 2/2] kill_pid_info: don't take now unneeded tasklist_lock
Date: Mon, 17 Mar 2008 20:01:24 +0300 [thread overview]
Message-ID: <20080317170124.GA115@tv-sign.ru> (raw)
In-Reply-To: <47DE5665.2030802@bk.jp.nec.com>
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@tv-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.
next prev parent reply other threads:[~2008-03-17 16:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-04 18:57 [RFC,PATCH 2/2] kill_pid_info: don't take now unneeded tasklist_lock Oleg Nesterov
2008-03-06 10:56 ` Roland McGrath
2008-03-17 11:30 ` Atsushi Tsuji
2008-03-17 17:01 ` Oleg Nesterov [this message]
2008-03-18 14:44 ` [PATCH] signals: check_kill_permission: check session under tasklist_lock Oleg Nesterov
2008-03-18 20:03 ` serge
2008-03-18 20:17 ` Oleg Nesterov
2008-03-18 23:14 ` serge
2008-03-19 2:19 ` Atsushi Tsuji
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