From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755325Ab3IKFgB (ORCPT ); Wed, 11 Sep 2013 01:36:01 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:22176 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754571Ab3IKE5T (ORCPT ); Wed, 11 Sep 2013 00:57:19 -0400 X-Authority-Analysis: v=2.0 cv=V4T/IJbi c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Ciwy3NGCPMMA:10 a=soAccpzBKCgA:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=g8gM5mogDLoA:10 a=pGLkceISAAAA:8 a=i0EeH86SAAAA:8 a=VwQbUJbxAAAA:8 a=ag1SF4gXAAAA:8 a=geoZPReg1UnzQyajuMYA:9 a=MSl-tDqOz04A:10 a=hPjdaMEvmhQA:10 a=1TSTQ8KKaH4A:10 a=jeBq3FmKZ4MA:10 a=xzBpS61pBPIHkZr6:21 a=HP5eGXHrFAa8TZB6:21 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-Id: <20130911042916.643722187@goodmis.org> User-Agent: quilt/0.60-1 Date: Wed, 11 Sep 2013 00:29:33 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Jiang Liu , Greg Kroah-Hartman Subject: [146/251] zram: use zram->lock to protect zram_free_page() in swap free notify path References: <20130911042707.738353451@goodmis.org> Content-Disposition: inline; filename=0146-zram-use-zram-lock-to-protect-zram_free_page-in-swap.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.6.11.9-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiang Liu [ Upstream commit 57ab048532c0d975538cebd4456491b5c34248f4 ] 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 Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Steven Rostedt --- 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 38a1b44..4322baf 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -622,7 +622,9 @@ 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 572c0b1..a6eb5d9 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; -- 1.7.10.4