From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Paul Mackerras , Yasuaki Ishimatsu , Pekka Enberg , David Rientjes , Christoph Lameter , Joonsoo Kim , Andrew Morton , Linus Torvalds Subject: [PATCH 3.17 07/47] slab: fix nodeid bounds check for non-contiguous node IDs Date: Sun, 14 Dec 2014 12:20:42 -0800 Message-Id: <20141214201818.781357387@linuxfoundation.org> In-Reply-To: <20141214201818.552715149@linuxfoundation.org> References: <20141214201818.552715149@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paul Mackerras commit 7c3fbbdd04a681a1992ad6a3d7a36a63ff668753 upstream. 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! Call Trace: .____cache_alloc_node+0x5c/0x270 (unreliable) .kmem_cache_alloc_node_trace+0xdc/0x360 .init_list+0x3c/0x128 .kmem_cache_init+0x1dc/0x258 .start_kernel+0x2a0/0x568 start_here_common+0x20/0xa8 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. Fixes: 14e50c6a9bc2 ("mm: slab: Verify the nodeid passed to ____cache_alloc_node") Signed-off-by: Paul Mackerras Reviewed-by: Yasuaki Ishimatsu Reviewed-by: Pekka Enberg Acked-by: David Rientjes Cc: Christoph Lameter Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/slab.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/slab.c +++ b/mm/slab.c @@ -3108,7 +3108,7 @@ static void *____cache_alloc_node(struct 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);