From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f173.google.com (mail-ig0-f173.google.com [209.85.213.173]) by kanga.kvack.org (Postfix) with ESMTP id 9345D6B0035 for ; Wed, 16 Jul 2014 20:36:52 -0400 (EDT) Received: by mail-ig0-f173.google.com with SMTP id h18so5090511igc.12 for ; Wed, 16 Jul 2014 17:36:52 -0700 (PDT) Received: from mail-ig0-x230.google.com (mail-ig0-x230.google.com [2607:f8b0:4001:c05::230]) by mx.google.com with ESMTPS id s11si2336512ich.19.2014.07.16.17.36.51 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 16 Jul 2014 17:36:51 -0700 (PDT) Received: by mail-ig0-f176.google.com with SMTP id hn18so5041809igb.9 for ; Wed, 16 Jul 2014 17:36:51 -0700 (PDT) Date: Wed, 16 Jul 2014 17:36:49 -0700 (PDT) From: David Rientjes Subject: [patch] mm, writeback: prevent race when calculating dirty limits Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Rik van Riel , stable@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Setting vm_dirty_bytes and dirty_background_bytes is not protected by any serialization. Therefore, it's possible for either variable to change value after the test in global_dirty_limits() to determine whether available_memory needs to be initialized or not. Always ensure that available_memory is properly initialized. Cc: stable@vger.kernel.org Signed-off-by: David Rientjes --- mm/page-writeback.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -261,14 +261,11 @@ static unsigned long global_dirtyable_memory(void) */ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) { + const unsigned long available_memory = global_dirtyable_memory(); unsigned long background; unsigned long dirty; - unsigned long uninitialized_var(available_memory); struct task_struct *tsk; - if (!vm_dirty_bytes || !dirty_background_bytes) - available_memory = global_dirtyable_memory(); - if (vm_dirty_bytes) dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); else -- 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