From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id 1EAE26B01EF for ; Thu, 1 Apr 2010 09:15:59 -0400 (EDT) Date: Thu, 1 Apr 2010 15:13:57 +0200 From: Oleg Nesterov Subject: [PATCH 1/1] oom: fix the unsafe usage of badness() in proc_oom_score() Message-ID: <20100401131357.GB11291@redhat.com> References: <20100328162821.GA16765@redhat.com> <20100329112111.GA16971@redhat.com> <20100330163909.GA16884@redhat.com> <20100331091628.GA11438@redhat.com> <20100331201746.GC11635@redhat.com> <20100401131321.GA11291@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100401131321.GA11291@redhat.com> Sender: owner-linux-mm@kvack.org To: David Rientjes , Andrew Morton , Linus Torvalds Cc: anfei , KOSAKI Motohiro , nishimura@mxp.nes.nec.co.jp, KAMEZAWA Hiroyuki , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@kernel.org List-ID: proc_oom_score(task) have a reference to task_struct, but that is all. If this task was already released before we take tasklist_lock - we can't use task->group_leader, it points to nowhere - it is not safe to call badness() even if this task is ->group_leader, has_intersects_mems_allowed() assumes it is safe to iterate over ->thread_group list. - even worse, badness() can hit ->signal == NULL Add the pid_alive() check to ensure __unhash_process() was not called. Also, use "task" instead of task->group_leader. badness() should return the same result for any sub-thread. Currently this is not true, but this should be changed anyway. Signed-off-by: Oleg Nesterov --- fs/proc/base.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- TTT/fs/proc/base.c~PROC_OOM_SCORE 2010-03-11 13:11:50.000000000 +0100 +++ TTT/fs/proc/base.c 2010-04-01 14:41:17.000000000 +0200 @@ -442,12 +442,13 @@ static const struct file_operations proc unsigned long badness(struct task_struct *p, unsigned long uptime); static int proc_oom_score(struct task_struct *task, char *buffer) { - unsigned long points; + unsigned long points = 0; struct timespec uptime; do_posix_clock_monotonic_gettime(&uptime); read_lock(&tasklist_lock); - points = badness(task->group_leader, uptime.tv_sec); + if (pid_alive(task)) + points = badness(task, uptime.tv_sec); read_unlock(&tasklist_lock); return sprintf(buffer, "%lu\n", points); } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org