From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id 16A436B0069 for ; Sun, 30 Nov 2014 20:18:34 -0500 (EST) Received: by mail-pa0-f45.google.com with SMTP id lj1so9943838pab.18 for ; Sun, 30 Nov 2014 17:18:33 -0800 (PST) Received: from fgwmail5.fujitsu.co.jp (fgwmail5.fujitsu.co.jp. [192.51.44.35]) by mx.google.com with ESMTPS id wb7si26529976pab.156.2014.11.30.17.18.31 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Sun, 30 Nov 2014 17:18:32 -0800 (PST) Received: from kw-mxoi2.gw.nic.fujitsu.com (unknown [10.0.237.143]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id 41BCD3EE13E for ; Mon, 1 Dec 2014 10:18:30 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by kw-mxoi2.gw.nic.fujitsu.com (Postfix) with ESMTP id 3A062AC039A for ; Mon, 1 Dec 2014 10:18:29 +0900 (JST) Received: from g01jpfmpwyt01.exch.g01.fujitsu.local (g01jpfmpwyt01.exch.g01.fujitsu.local [10.128.193.38]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id DA291E08002 for ; Mon, 1 Dec 2014 10:18:28 +0900 (JST) Message-ID: <547BC199.6070200@jp.fujitsu.com> Date: Mon, 1 Dec 2014 10:17:13 +0900 From: Yasuaki Ishimatsu MIME-Version: 1.0 Subject: Re: [PATCH] slab: Fix nodeid bounds check for non-contiguous node IDs References: <20141130221606.GA25929@iris.ozlabs.ibm.com> <547BB2F0.5040708@jp.fujitsu.com> <20141201004210.GA11234@drongo> In-Reply-To: <20141201004210.GA11234@drongo> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Paul Mackerras Cc: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Pekka Enberg , linuxppc-dev@ozlabs.org, David Rientjes , Christoph Lameter , Joonsoo Kim (2014/12/01 9:42), Paul Mackerras wrote: > On Mon, Dec 01, 2014 at 09:14:40AM +0900, Yasuaki Ishimatsu wrote: >> (2014/12/01 7:16), Paul Mackerras wrote: >>> 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. >> >> Do you have the call trace? If you have it, please add it in the description. > > I can get it easily enough. > >>> 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 >> >> Do you need to backport it into -stable kernels? > > It does need to go to stable, yes, for 3.10 and later. > >>> --- >>> 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); >> >> How about use: >> VM_BUG_ON(!node_online(nodeid)); > > That would not be better, since node_online() doesn't bounds-check its > argument. > Ah. You are right. >> When allocating the memory, the node of the memory being allocated must be >> online. But your code cannot check the condition. > > The following two lines: > >>> n = get_node(cachep, nodeid); >>> BUG_ON(!n); > > effectively check that condition already, as I tried to explain in the > commit message. O.K. I understood. Thansk, Yasuaki Ishimatsu > > Regards, > Paul. > -- 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