From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756134Ab3FDQIo (ORCPT ); Tue, 4 Jun 2013 12:08:44 -0400 Received: from mail-pd0-f181.google.com ([209.85.192.181]:53255 "EHLO mail-pd0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755935Ab3FDQIj (ORCPT ); Tue, 4 Jun 2013 12:08:39 -0400 From: Jiang Liu To: Greg Kroah-Hartman , Nitin Gupta , Minchan Kim , Jerome Marchand Cc: Yijing Wang , Jiang Liu , devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 03/10] zram: use zram->lock to protect zram_free_page() in swap free notify path Date: Wed, 5 Jun 2013 00:06:01 +0800 Message-Id: <1370361968-8764-3-git-send-email-jiang.liu@huawei.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1370361968-8764-1-git-send-email-jiang.liu@huawei.com> References: <1370361968-8764-1-git-send-email-jiang.liu@huawei.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org zram_free_page() is protected by down_write(&zram->lock) when called by zram_bvec_write(), but there's no such protection when called by zram_slot_free_notify(), which may cause wrong states to zram object. There are two possible consequences of this issue: 1) It may cause invalid memory access if we read from a zram device used as swap device. (Not sure whether it's legal to make read/write requests to a zram device used as swap device.) 2) It may cause some fields (bad_compress, good_compress, pages_stored) in zram->stats wrong if the swap layer makes concurrently call to zram_slot_free_notify(). So enhance zram_slot_free_notify() to acquire writer lock on zram->lock before calling zram_free_page(). Signed-off-by: Jiang Liu Cc: stable@vger.kernel.org --- drivers/staging/zram/zram_drv.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index 5a2f20b..847d207 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -582,7 +582,9 @@ static void zram_slot_free_notify(struct block_device *bdev, struct zram *zram; zram = bdev->bd_disk->private_data; + down_write(&zram->lock); zram_free_page(zram, index); + up_write(&zram->lock); zram_stat64_inc(zram, &zram->stats.notify_free); } -- 1.8.1.2