This is a note to let you know that I've just added the patch titled
slab: fix nodeid bounds check for non-contiguous node IDs
to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
slab-fix-nodeid-bounds-check-for-non-contiguous-node-ids.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7c3fbbdd04a681a1992ad6a3d7a36a63ff668753 Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@xxxxxxxxx>
Date: Tue, 2 Dec 2014 15:59:48 -0800
Subject: slab: fix nodeid bounds check for non-contiguous node IDs
From: Paul Mackerras <paulus@xxxxxxxxx>
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 <paulus@xxxxxxxxx>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Reviewed-by: Pekka Enberg <penberg@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
Patches currently in stable-queue which might be from paulus@xxxxxxxxx are
queue-3.17/slab-fix-nodeid-bounds-check-for-non-contiguous-node-ids.patch
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