From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758217Ab3BUWIS (ORCPT ); Thu, 21 Feb 2013 17:08:18 -0500 Received: from mx4-phx2.redhat.com ([209.132.183.25]:44391 "EHLO mx4-phx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757543Ab3BUWIA (ORCPT ); Thu, 21 Feb 2013 17:08:00 -0500 Date: Thu, 21 Feb 2013 17:07:58 -0500 (EST) From: Aaron Tomlin To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Rik Message-ID: <943811281.6485888.1361484478519.JavaMail.root@redhat.com> In-Reply-To: <1285971995.6305502.1361465165007.JavaMail.root@redhat.com> Subject: [PATCH] mm: slab: Verify the nodeid passed to ____cache_alloc_node MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.36.4.24] X-Mailer: Zimbra 7.2.0_GA_2669 (ZimbraWebClient - GC24 (Linux)/7.2.0_GA_2669) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, The addition of this BUG_ON should make debugging easier. While I understand that this code path is "hot", surely it is better to assert the condition than to wait until some random NULL pointer dereference or page fault. If the caller passes an invalid nodeid, at this stage in my opinion it's already a BUG. Cheers, Aaron ---8<--- mm: slab: Verify the nodeid passed to ____cache_alloc_node If the nodeid is > num_online_nodes() this can cause an Oops and a panic(). The purpose of this patch is to assert if this condition is true to aid debugging efforts rather than some random NULL pointer dereference or page fault. Signed-off-by: Aaron Tomlin slab.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/slab.c b/mm/slab.c index e7667a3..735e8bd 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3412,6 +3412,7 @@ static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, void *obj; int x; + BUG_ON(nodeid > num_online_nodes()); l3 = cachep->nodelists[nodeid]; BUG_ON(!l3);