Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932605Ab2ENWaE (ORCPT ); Mon, 14 May 2012 18:30:04 -0400 Received: from na3sys009aog124.obsmtp.com ([74.125.149.151]:36545 "HELO na3sys009aog124.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S932528Ab2ENWaC (ORCPT ); Mon, 14 May 2012 18:30:02 -0400 From: Pravin B Shelar To: cl@linux.com, penberg@kernel.org, mpm@selenic.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, jesse@nicira.com, abhide@nicira.com, Pravin B Shelar Subject: [PATCH v2] mm: Fix slab->page _count corruption. Date: Mon, 14 May 2012 15:29:57 -0700 Message-Id: <1337034597-1826-1-git-send-email-pshelar@nicira.com> X-Mailer: git-send-email 1.7.10 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1407 Lines: 44 On arches that do not support this_cpu_cmpxchg_double slab_lock is used to do atomic cmpxchg() on double word which contains page->_count. page count can be changed from get_page() or put_page() without taking slab_lock. That corrupts page counter. Following patch fixes it by moving page->_count out of cmpxchg_double data. So that slub does no change it while updating slub meta-data in struct page. Reported-by: Amey Bhide Signed-off-by: Pravin B Shelar --- include/linux/mm_types.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index dad95bd..5f558dc 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -57,8 +57,16 @@ struct page { }; union { +#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \ + defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) /* Used for cmpxchg_double in slub */ unsigned long counters; +#else + /* Keep _count separate from slub cmpxchg_double data, + * As rest of double word is protected by slab_lock + * but _count is not. */ + unsigned counters; +#endif struct { -- 1.7.10 -- 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/