Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967701Ab3HICLA (ORCPT ); Thu, 8 Aug 2013 22:11:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:55787 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967660Ab3HIB7M (ORCPT ); Thu, 8 Aug 2013 21:59:12 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jiang Liu Subject: [ 061/102] zram: use zram->lock to protect zram_free_page() in swap free notify path Date: Thu, 8 Aug 2013 18:57:37 -0700 Message-Id: <20130809015024.585003988@linuxfoundation.org> X-Mailer: git-send-email 1.8.3.rc0.20.gb99dd2e In-Reply-To: <20130809015010.208118575@linuxfoundation.org> References: <20130809015010.208118575@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2185 Lines: 62 3.10-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 --- drivers/staging/zram/zram_drv.c | 2 ++ drivers/staging/zram/zram_drv.h | 5 +++-- 2 files changed, 5 insertions(+), 2 deletions(-) --- 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 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); } --- a/drivers/staging/zram/zram_drv.h +++ b/drivers/staging/zram/zram_drv.h @@ -93,8 +93,9 @@ struct zram_meta { struct zram { struct zram_meta *meta; 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/