From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f200.google.com (mail-lb0-f200.google.com [209.85.217.200]) by kanga.kvack.org (Postfix) with ESMTP id 7FD366B007E for ; Fri, 27 May 2016 04:01:25 -0400 (EDT) Received: by mail-lb0-f200.google.com with SMTP id rs7so50535737lbb.2 for ; Fri, 27 May 2016 01:01:25 -0700 (PDT) Received: from mout.kundenserver.de (mout.kundenserver.de. [212.227.126.133]) by mx.google.com with ESMTPS id v8si24300548wjf.38.2016.05.27.01.01.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 27 May 2016 01:01:24 -0700 (PDT) From: Arnd Bergmann Subject: [PATCH] oom_reaper: don't call mmput_async() on uninitialized mm Date: Fri, 27 May 2016 10:00:48 +0200 Message-Id: <1464336081-994232-1-git-send-email-arnd@arndb.de> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Michal Hocko Cc: Arnd Bergmann , David Rientjes , Tetsuo Handa , Johannes Weiner , Oleg Nesterov , linux-mm@kvack.org, linux-kernel@vger.kernel.org The change to the oom_reaper to hold a mutex inside __oom_reap_task() accidentally started calling mmput_async() on the local mm before that variable got initialized, as reported by gcc in linux-next: mm/oom_kill.c: In function '__oom_reap_task': mm/oom_kill.c:537:2: error: 'mm' may be used uninitialized in this function [-Werror=maybe-uninitialized] This rearranges the code slightly back to the state before patch but leaves the lock in place. The error handling in the function still looks a bit confusing and could probably be improved but I could not come up with a solution that made me happy for now. Signed-off-by: Arnd Bergmann Fixes: mmotm ("oom_reaper: close race with exiting task") --- mm/oom_kill.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 1685890d424e..255cb5f48019 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -447,7 +447,7 @@ static bool __oom_reap_task(struct task_struct *tsk) struct task_struct *p; struct zap_details details = {.check_swap_entries = true, .ignore_dirty = true}; - bool ret = true; + bool ret; /* * We have to make sure to not race with the victim exit path @@ -472,13 +472,16 @@ static bool __oom_reap_task(struct task_struct *tsk) * is no mm. */ p = find_lock_task_mm(tsk); - if (!p) - goto unlock_oom; + if (!p) { + mutex_unlock(&oom_lock); + return true; + } mm = p->mm; if (!atomic_inc_not_zero(&mm->mm_users)) { task_unlock(p); - goto unlock_oom; + mutex_unlock(&oom_lock); + return true; } task_unlock(p); @@ -527,6 +530,7 @@ static bool __oom_reap_task(struct task_struct *tsk) * to release its memory. */ set_bit(MMF_OOM_REAPED, &mm->flags); + ret = true; unlock_oom: mutex_unlock(&oom_lock); /* -- 2.7.0 -- 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