From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id 637BC6B01F0 for ; Tue, 30 Mar 2010 12:41:21 -0400 (EDT) Date: Tue, 30 Mar 2010 18:39:09 +0200 From: Oleg Nesterov Subject: [PATCH] oom: fix the unsafe proc_oom_score()->badness() call Message-ID: <20100330163909.GA16884@redhat.com> References: <1269447905-5939-1-git-send-email-anfei.zhou@gmail.com> <20100326150805.f5853d1c.akpm@linux-foundation.org> <20100326223356.GA20833@redhat.com> <20100328145528.GA14622@desktop> <20100328162821.GA16765@redhat.com> <20100329112111.GA16971@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: David Rientjes , anfei , KOSAKI Motohiro , nishimura@mxp.nes.nec.co.jp, KAMEZAWA Hiroyuki , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.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. Add the pid_alive() check to ensure __unhash_process() was not called. Note: I think we shouldn't use ->group_leader, badness() should return the same result for any sub-thread. However this is not true currently, and I think that ->mm check and list_for_each_entry(p->children) in badness are not right. Signed-off-by: Oleg Nesterov --- fs/proc/base.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- 34-rc1/fs/proc/base.c~OOM_SCORE 2010-03-22 16:36:28.000000000 +0100 +++ 34-rc1/fs/proc/base.c 2010-03-30 18:23:50.000000000 +0200 @@ -430,12 +430,13 @@ 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->group_leader, 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