From patchwork Wed Jul 17 22:45:42 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kamal Mostafa X-Patchwork-Id: 259797 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id DED2A2C008C for ; Thu, 18 Jul 2013 08:50:21 +1000 (EST) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1UzaY2-0006QT-VF; Wed, 17 Jul 2013 22:50:14 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1UzaWZ-0006Ej-82 for kernel-team@lists.ubuntu.com; Wed, 17 Jul 2013 22:48:43 +0000 Received: from c-67-160-231-162.hsd1.ca.comcast.net ([67.160.231.162] helo=fourier) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1UzaWY-0008Bx-Sl; Wed, 17 Jul 2013 22:48:43 +0000 Received: from kamal by fourier with local (Exim 4.80) (envelope-from ) id 1UzaWW-0002Iw-IE; Wed, 17 Jul 2013 15:48:40 -0700 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com 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 Cc: Greg Kroah-Hartman , Jiang Liu X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com 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;