From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx183.postini.com [74.125.245.183]) by kanga.kvack.org (Postfix) with SMTP id D71DF6B0006 for ; Fri, 18 Jan 2013 09:52:58 -0500 (EST) Date: Fri, 18 Jan 2013 14:52:57 +0000 From: Christoph Lameter Subject: Re: [RFC][PATCH v2] slub: Keep page and object in sync in slab_alloc_node() In-Reply-To: <20130118044242.GA18665@lge.com> Message-ID: <0000013c4e25f885-c4f6e914-525b-4ffb-8272-f41ba9dd02d3-000000@email.amazonses.com> References: <1358446258.23211.32.camel@gandalf.local.home> <1358447864.23211.34.camel@gandalf.local.home> <0000013c4a69a2cf-1a19a6f6-e6a3-4f06-99a4-10fdd4b9aca2-000000@email.amazonses.com> <1358458996.23211.46.camel@gandalf.local.home> <0000013c4a7e7fbf-c51fd42a-2455-4fec-bb37-915035956f05-000000@email.amazonses.com> <1358462763.23211.57.camel@gandalf.local.home> <1358464245.23211.62.camel@gandalf.local.home> <1358464837.23211.66.camel@gandalf.local.home> <1358468598.23211.67.camel@gandalf.local.home> <1358468924.23211.69.camel@gandalf.local.home> <20130118044242.GA18665@lge.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Steven Rostedt , LKML , linux-mm , Andrew Morton , Pekka Enberg , Matt Mackall , Thomas Gleixner , RT , Clark Williams , John Kacur , "Luis Claudio R. Goncalves" On Fri, 18 Jan 2013, Joonsoo Kim wrote: > How about this? The easiest fix is to just check for NULL in node_match since a similar situation can occur in slab_free. Subject: slub: Do not dereference NULL pointer in node_match The variables accessed in slab_alloc are volatile and therefore the page pointer passed to node_match can be NULL. The processing of data in slab_alloc is tentative until either the cmpxchg succeeds or the __slab_alloc slowpath is invoked. Both are able to perform the same allocation from the freelist. Check for the NULL pointer in node_match. A false positive will lead to a retry of the loop in slab_alloc(). Signed-off-by: Christoph Lameter Index: linux/mm/slub.c =================================================================== --- linux.orig/mm/slub.c 2013-01-18 08:47:29.198954250 -0600 +++ linux/mm/slub.c 2013-01-18 08:47:40.579126371 -0600 @@ -2041,7 +2041,7 @@ static void flush_all(struct kmem_cache static inline int node_match(struct page *page, int node) { #ifdef CONFIG_NUMA - if (node != NUMA_NO_NODE && page_to_nid(page) != node) + if (page && (node != NUMA_NO_NODE && page_to_nid(page) != node)) return 0; #endif return 1; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org