From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757553AbbAIKcb (ORCPT ); Fri, 9 Jan 2015 05:32:31 -0500 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:44483 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751726AbbAIKc2 (ORCPT ); Fri, 9 Jan 2015 05:32:28 -0500 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Anton Vorontsov , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 17/78] mm/vmpressure.c: fix race in vmpressure_work_fn() Date: Fri, 9 Jan 2015 11:31:26 +0100 Message-Id: <5a40e10cc3479a28bac0d4ca3134df7052cb46df.1420799385.git.jslaby@suse.cz> X-Mailer: git-send-email 2.2.1 In-Reply-To: <72002f1f248c28d1715d10454190e209d5a20fe1.1420799385.git.jslaby@suse.cz> References: <72002f1f248c28d1715d10454190e209d5a20fe1.1420799385.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrew Morton 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 91b57191cfd152c02ded0745250167d0263084f8 upstream. In some android devices, there will be a "divide by zero" exception. vmpr->scanned could be zero before spin_lock(&vmpr->sr_lock). Addresses https://bugzilla.kernel.org/show_bug.cgi?id=88051 [akpm@linux-foundation.org: neaten] Reported-by: ji_ang Cc: Anton Vorontsov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby --- mm/vmpressure.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/vmpressure.c b/mm/vmpressure.c index e0f62837c3f4..c98b14ee69d6 100644 --- a/mm/vmpressure.c +++ b/mm/vmpressure.c @@ -164,6 +164,7 @@ static void vmpressure_work_fn(struct work_struct *work) unsigned long scanned; unsigned long reclaimed; + spin_lock(&vmpr->sr_lock); /* * Several contexts might be calling vmpressure(), so it is * possible that the work was rescheduled again before the old @@ -172,11 +173,12 @@ static void vmpressure_work_fn(struct work_struct *work) * here. No need for any locks here since we don't care if * vmpr->reclaimed is in sync. */ - if (!vmpr->scanned) + scanned = vmpr->scanned; + if (!scanned) { + spin_unlock(&vmpr->sr_lock); return; + } - spin_lock(&vmpr->sr_lock); - scanned = vmpr->scanned; reclaimed = vmpr->reclaimed; vmpr->scanned = 0; vmpr->reclaimed = 0; -- 2.2.1