From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753923Ab2IQBNy (ORCPT ); Sun, 16 Sep 2012 21:13:54 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33672 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753008Ab2IQAu2 (ORCPT ); Sun, 16 Sep 2012 20:50:28 -0400 Message-Id: <20120917003640.612138396@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Mon, 17 Sep 2012 01:38:09 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Seth Jennings , Konrad Rzeszutek Wilk , Minchan Kim , Greg Kroah-Hartman Subject: [ 104/135] staging: zcache: fix cleancache race condition with shrinker In-Reply-To: <20120917003625.784119135@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Seth Jennings commit 6d7d9798ad5c97ee4e911dd070dc12dc5ae55bd0 upstream. This patch fixes a race condition that results in memory corruption when using cleancache. The race exists between the zcache shrinker handler, shrink_zcache_memory() and cleancache_get_page(). In most cases, the shrinker will both evict a zbpg from its buddy list and flush it from tmem before a cleancache_get_page() occurs on that page. A subsequent cleancache_get_page() will fail in the tmem layer. In the rare case that two occur together and the cleancache_get_page() path gets through the tmem layer before the shrinker path can flush tmem, zbud_decompress() does a check to see if the zbpg is a "zombie", i.e. not on a buddy list, which means the shrinker is in the process of reclaiming it. If the zbpg is a zombie, zbud_decompress() returns -EINVAL. However, this return code is being ignored by the caller, zcache_pampd_get_data_and_free(), which results in the caller of cleancache_get_page() thinking that the page has been properly retrieved when it has not. This patch modifies zcache_pampd_get_data_and_free() to convey the failure up the stack so that the caller of cleancache_get_page() knows the page retrieval failed. This needs to be applied to stable trees as well. zcache-main.c was named zcache.c before v3.1, so I'm not sure how you want to handle trees earlier than that. Signed-off-by: Seth Jennings Reviewed-by: Konrad Rzeszutek Wilk Reviewed-by: Minchan Kim Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/staging/zcache/zcache-main.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c index c214977..52b43b7 100644 --- a/drivers/staging/zcache/zcache-main.c +++ b/drivers/staging/zcache/zcache-main.c @@ -1251,13 +1251,12 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *bufsize, bool raw, void *pampd, struct tmem_pool *pool, struct tmem_oid *oid, uint32_t index) { - int ret = 0; - BUG_ON(!is_ephemeral(pool)); - zbud_decompress((struct page *)(data), pampd); + if (zbud_decompress((struct page *)(data), pampd) < 0) + return -EINVAL; zbud_free_and_delist((struct zbud_hdr *)pampd); atomic_dec(&zcache_curr_eph_pampd_count); - return ret; + return 0; } /*