From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id A40ED6B0069 for ; Sun, 30 Nov 2014 17:16:17 -0500 (EST) Received: by mail-pa0-f51.google.com with SMTP id ey11so9706058pad.24 for ; Sun, 30 Nov 2014 14:16:17 -0800 (PST) Received: from ozlabs.org (ozlabs.org. [2401:3900:2:1::2]) by mx.google.com with ESMTPS id cc14si26097095pac.137.2014.11.30.14.16.15 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 30 Nov 2014 14:16:16 -0800 (PST) Date: Mon, 1 Dec 2014 09:16:07 +1100 From: Paul Mackerras Subject: [PATCH] slab: Fix nodeid bounds check for non-contiguous node IDs Message-ID: <20141130221606.GA25929@iris.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton The bounds check for nodeid in ____cache_alloc_node gives false positives on machines where the node IDs are not contiguous, leading to a panic at boot time. For example, on a POWER8 machine the node IDs are typically 0, 1, 16 and 17. This means that num_online_nodes() returns 4, so when ____cache_alloc_node is called with nodeid = 16 the VM_BUG_ON triggers. To fix this, we instead compare the nodeid with MAX_NUMNODES, and additionally make sure it isn't negative (since nodeid is an int). The check is there mainly to protect the array dereference in the get_node() call in the next line, and the array being dereferenced is of size MAX_NUMNODES. If the nodeid is in range but invalid, the BUG_ON in the next line will catch that. Signed-off-by: Paul Mackerras --- diff --git a/mm/slab.c b/mm/slab.c index eb2b2ea..f34e053 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3076,7 +3076,7 @@ static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, void *obj; int x; - VM_BUG_ON(nodeid > num_online_nodes()); + VM_BUG_ON(nodeid < 0 || nodeid >= MAX_NUMNODES); n = get_node(cachep, nodeid); BUG_ON(!n); -- 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