Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932499AbaLAVGN (ORCPT ); Mon, 1 Dec 2014 16:06:13 -0500 Received: from mail-ie0-f173.google.com ([209.85.223.173]:48522 "EHLO mail-ie0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932241AbaLAVGM (ORCPT ); Mon, 1 Dec 2014 16:06:12 -0500 Date: Mon, 1 Dec 2014 13:06:09 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Paul Mackerras cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Christoph Lameter , Pekka Enberg , Joonsoo Kim , Andrew Morton Subject: Re: [PATCH v2] slab: Fix nodeid bounds check for non-contiguous node IDs In-Reply-To: <20141201042844.GB11234@drongo> Message-ID: References: <20141201042844.GB11234@drongo> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 1 Dec 2014, 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, like this: > > kernel BUG at /home/paulus/kernel/kvm/mm/slab.c:3079! > Oops: Exception in kernel mode, sig: 5 [#1] > SMP NR_CPUS=1024 NUMA PowerNV > Modules linked in: > CPU: 0 PID: 0 Comm: swapper Not tainted 3.18.0-rc5-kvm+ #17 > task: c0000000013ba230 ti: c000000001494000 task.ti: c000000001494000 > NIP: c000000000264f6c LR: c000000000264f5c CTR: 0000000000000000 > REGS: c0000000014979a0 TRAP: 0700 Not tainted (3.18.0-rc5-kvm+) > MSR: 9000000002021032 CR: 28000448 XER: 20000000 > CFAR: c00000000047e978 SOFTE: 0 > GPR00: c000000000264f5c c000000001497c20 c000000001499d48 0000000000000004 > GPR04: 0000000000000100 0000000000000010 0000000000000068 ffffffffffffffff > GPR08: 0000000000000000 0000000000000001 00000000082d0000 c000000000cca5a8 > GPR12: 0000000048000448 c00000000fda0000 000001003bd44ff0 0000000010020578 > GPR16: 000001003bd44ff8 000001003bd45000 0000000000000001 0000000000000000 > GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000010 > GPR24: c000000ffe000080 c000000000c824ec 0000000000000068 c000000ffe000080 > GPR28: 0000000000000010 c000000ffe000080 0000000000000010 0000000000000000 > NIP [c000000000264f6c] .____cache_alloc_node+0x6c/0x270 > LR [c000000000264f5c] .____cache_alloc_node+0x5c/0x270 > Call Trace: > [c000000001497c20] [c000000000264f5c] .____cache_alloc_node+0x5c/0x270 (unreliable) > [c000000001497cf0] [c00000000026552c] .kmem_cache_alloc_node_trace+0xdc/0x360 > [c000000001497dc0] [c000000000c824ec] .init_list+0x3c/0x128 > [c000000001497e50] [c000000000c827b4] .kmem_cache_init+0x1dc/0x258 > [c000000001497ef0] [c000000000c54090] .start_kernel+0x2a0/0x568 > [c000000001497f90] [c000000000008c6c] start_here_common+0x20/0xa8 > Instruction dump: > 7c7d1b78 7c962378 4bda4e91 60000000 3c620004 38800100 386370d8 48219959 > 60000000 7f83e000 7d301026 5529effe <0b090000> 393c0010 79291f24 7d3d4a14 > > 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 (for > example if the node is off-line), the BUG_ON in the next line will > catch that. > > Signed-off-by: Paul Mackerras Acked-by: David Rientjes -- 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/