From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934776Ab3GQXho (ORCPT ); Wed, 17 Jul 2013 19:37:44 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:56210 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757518Ab3GQWso (ORCPT ); Wed, 17 Jul 2013 18:48:44 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Jiang Liu , Greg Kroah-Hartman , Luis Henriques Subject: [PATCH 010/145] zram: use zram->lock to protect zram_free_page() in swap free notify path Date: Wed, 17 Jul 2013 15:45:42 -0700 Message-Id: <1374101277-7915-11-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1374101277-7915-1-git-send-email-kamal@canonical.com> References: <1374101277-7915-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.8.13.5 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiang Liu commit 57ab048532c0d975538cebd4456491b5c34248f4 upstream. zram_slot_free_notify() is free-running without any protection from concurrent operations. So there are race conditions between zram_bvec_read()/zram_bvec_write() and zram_slot_free_notify(), and possible consequences include: 1) Trigger BUG_ON(!handle) on zram_bvec_write() side. 2) Access to freed pages on zram_bvec_read() side. 3) Break some fields (bad_compress, good_compress, pages_stored) in zram->stats 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 Signed-off-by: Greg Kroah-Hartman [ luis: backported to 3.8: adjusted context ] Signed-off-by: Luis Henriques --- drivers/staging/zram/zram_drv.c | 2 ++ drivers/staging/zram/zram_drv.h | 5 +++-- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index c9c1e0e..0113897 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -615,7 +615,9 @@ 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); } diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h index df2eec4..4265ab4 100644 --- a/drivers/staging/zram/zram_drv.h +++ b/drivers/staging/zram/zram_drv.h @@ -92,8 +92,9 @@ struct zram { void *compress_buffer; struct table *table; spinlock_t stat64_lock; /* protect 64-bit stats */ - struct rw_semaphore lock; /* protect compression buffers and table - * against concurrent read and writes */ + struct rw_semaphore lock; /* protect compression buffers, table, + * 32bit stat counters against concurrent + * notifications, reads and writes */ struct request_queue *queue; struct gendisk *disk; int init_done; -- 1.8.1.2