From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933112AbbI3S1Z (ORCPT ); Wed, 30 Sep 2015 14:27:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55419 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933054AbbI3S1V (ORCPT ); Wed, 30 Sep 2015 14:27:21 -0400 Date: Wed, 30 Sep 2015 20:24:11 +0200 From: Oleg Nesterov To: Andrew Morton Cc: David Rientjes , Kyle Walker , Michal Hocko , Stanislav Kozina , Tetsuo Handa , linux-kernel@vger.kernel.org Subject: [PATCH -mm v2 3/3] mm/oom_kill: fix the wrong task->mm == mm checks in oom_kill_process() Message-ID: <20150930182411.GA15250@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150930182341.GA15047@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Both "child->mm == mm" and "p->mm != mm" checks in oom_kill_process() are wrong. task->mm can be NULL if the task is the exited group leader. This means in particular that "kill sharing same memory" loop can miss a process with a zombie leader which uses the same ->mm. Note: the process_has_mm(child, p->mm) check is still not 100% correct, p->mm can be NULL too. This is minor, but probably deserves a fix or a comment anyway. Signed-off-by: Oleg Nesterov --- mm/oom_kill.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index c189ee5..034d219 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -483,6 +483,18 @@ void oom_killer_enable(void) oom_killer_disabled = false; } +static bool process_shares_mm(struct task_struct *p, struct mm_struct *mm) +{ + struct task_struct *t; + + for_each_thread(p, t) { + struct mm_struct *t_mm = READ_ONCE(t->mm); + if (t_mm) + return t_mm == mm; + } + return false; +} + #define K(x) ((x) << (PAGE_SHIFT-10)) /* * Must be called while holding a reference to p, which will be released upon @@ -530,7 +542,7 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p, list_for_each_entry(child, &t->children, sibling) { unsigned int child_points; - if (child->mm == p->mm) + if (process_shares_mm(child, p->mm)) continue; /* * oom_badness() returns 0 if the thread is unkillable @@ -584,7 +596,7 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p, */ rcu_read_lock(); for_each_process(p) { - if (p->mm != mm) + if (!process_shares_mm(p, mm)) continue; if (same_thread_group(p, victim)) continue; -- 2.4.3