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Subject[PATCH] x86/numa: kernel stack corruption fix
I got below kernel panic during kdump test on Thinkpad T420 laptop:

[ 0.000000] No NUMA configuration found
[ 0.000000] Faking a node at [mem 0x0000000000000000-0x0000000037ba4fff]
[ 0.000000] Kernel panic - not syncing: stack-protector: Kernel stack is cor
upted in: ffffffff81d21910 r
[ 0.000000]
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.0.0-rc6+ #44
[ 0.000000] Hardware name: LENOVO 4236NUC/4236NUC, BIOS 83ET76WW (1.46 ) 07/
5/2013 0
[ 0.000000] 0000000000000000 c70296ddd809e4f6 ffffffff81b67ce8 ffffffff817c
a26 2
[ 0.000000] 0000000000000000 ffffffff81a61c90 ffffffff81b67d68 ffffffff817b
8d2 c
[ 0.000000] 0000000000000010 ffffffff81b67d78 ffffffff81b67d18 c70296ddd809
4f6 e
[ 0.000000] Call Trace:
[ 0.000000] [<ffffffff817c2a26>] dump_stack+0x45/0x57
[ 0.000000] [<ffffffff817bc8d2>] panic+0xd0/0x204
[ 0.000000] [<ffffffff81d21910>] ? numa_clear_kernel_node_hotplug+0xe6/0xf2
[ 0.000000] [<ffffffff8107741b>] __stack_chk_fail+0x1b/0x20
[ 0.000000] [<ffffffff81d21910>] numa_clear_kernel_node_hotplug+0xe6/0xf2
[ 0.000000] [<ffffffff81d21e5d>] numa_init+0x1a5/0x520
[ 0.000000] [<ffffffff81d222b1>] x86_numa_init+0x19/0x3d
[ 0.000000] [<ffffffff81d22460>] initmem_init+0x9/0xb
[ 0.000000] [<ffffffff81d0d00c>] setup_arch+0x94f/0xc82
[ 0.000000] [<ffffffff81d05120>] ? early_idt_handlers+0x120/0x120
[ 0.000000] [<ffffffff817bd0bb>] ? printk+0x55/0x6b
[ 0.000000] [<ffffffff81d05120>] ? early_idt_handlers+0x120/0x120
[ 0.000000] [<ffffffff81d05d9b>] start_kernel+0xe8/0x4d6
[ 0.000000] [<ffffffff81d05120>] ? early_idt_handlers+0x120/0x120
[ 0.000000] [<ffffffff81d05120>] ? early_idt_handlers+0x120/0x120
[ 0.000000] [<ffffffff81d055ee>] x86_64_start_reservations+0x2a/0x2c
[ 0.000000] [<ffffffff81d05751>] x86_64_start_kernel+0x161/0x184
[ 0.000000] ---[ end Kernel panic - not syncing: stack-protector: Kernel sta
k is corrupted in: ffffffff81d21910 c
[ 0.000000]
PANIC: early exception 0d rip 10:ffffffff8105d2a6 error 7eb cr2 ffff8800371dd00
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.0.0-rc6+ #44 0
[ 0.000000] Hardware name: LENOVO 4236NUC/4236NUC, BIOS 83ET76WW (1.46 ) 07/
5/2013 0
[ 0.000000] 0000000000000000 c70296ddd809e4f6 ffffffff81b67c60 ffffffff817c
a26 2
[ 0.000000] 0000000000000096 ffffffff81a61c90 ffffffff81b67d68 fffffff00000
084 0000000000000a0d 0000000000000a00 0
[ 0.000000] Call Trace:
[ 0.000000] [<ffffffff817c2a26>] dump_stack+0x45/0x57
[ 0.000000] [<ffffffff81d051b0>] early_idt_handler+0x90/0xb7
[ 0.000000] [<ffffffff8105d2a6>] ? native_irq_enable+0x6/0x10
[ 0.000000] [<ffffffff817bc9c5>] ? panic+0x1c3/0x204
[ 0.000000] [<ffffffff81d21910>] ? numa_clear_kernel_node_hotplug+0xe6/0xf2
[ 0.000000] [<ffffffff8107741b>] __stack_chk_fail+0x1b/0x20
[ 0.000000] [<ffffffff81d21910>] numa_clear_kernel_node_hotplug+0xe6/0xf2
[ 0.000000] [<ffffffff81d21e5d>] numa_init+0x1a5/0x520
[ 0.000000] [<ffffffff81d222b1>] x86_numa_init+0x19/0x3d
[ 0.000000] [<ffffffff81d22460>] initmem_init+0x9/0xb
[ 0.000000] [<ffffffff81d0d00c>] setup_arch+0x94f/0xc82
[ 0.000000] [<ffffffff81d05120>] ? early_idt_handlers+0x120/0x120
[ 0.000000] [<ffffffff817bd0bb>] ? printk+0x55/0x6b
[ 0.000000] [<ffffffff81d05120>] ? early_idt_handlers+0x120/0x120
[ 0.000000] [<ffffffff81d05d9b>] start_kernel+0xe8/0x4d6
[ 0.000000] [<ffffffff81d05120>] ? early_idt_handlers+0x120/0x120
[ 0.000000] [<ffffffff81d05120>] ? early_idt_handlers+0x120/0x120
[ 0.000000] [<ffffffff81d055ee>] x86_64_start_reservations+0x2a/0x2c
[ 0.000000] [<ffffffff81d05751>] x86_64_start_kernel+0x161/0x184
[ 0.000000] RIP 0x46

This is caused by writing over end of numa mask bitmap.

numa_clear_kernel_node try to set node id in a mask bitmap, it iterating all
reserved region and assume every regions have valid nid. It is not true because
There's an exception for graphic memory quirks. see function trim_snb_memory
in arch/x86/kernel/setup.c

It is easily to reproduce the bug in kdump kernel because kdump kernel use
prereserved memory instead of whole memory, but kexec pass other reserved memory
ranges to 2nd kernel as well. like below in my test:
kdump kernel ram 0x2d000000 - 0x37bfffff
One of the reserved regions: 0x40000000 - 0x40100000

The above reserved region includes 0x40004000, a page excluded in
trim_snb_memory. For this memblock reserved region the nid is not set it is
still default value MAX_NUMNODES. later node_set callback will set bit
MAX_NUMNODES in nodemask bitmap thus stack corruption happen.

Fixing this by adding a check, do not call node_set in case nid is MAX_NUMNODES.

Signed-off-by: Dave Young <dyoung@redhat.com>
---
arch/x86/mm/numa.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- linux.orig/arch/x86/mm/numa.c
+++ linux/arch/x86/mm/numa.c
@@ -484,7 +484,8 @@ static void __init numa_clear_kernel_nod

/* Mark all kernel nodes. */
for_each_memblock(reserved, r)
- node_set(r->nid, numa_kernel_nodes);
+ if (r->nid != MAX_NUMNODES)
+ node_set(r->nid, numa_kernel_nodes);

/* Clear MEMBLOCK_HOTPLUG flag for memory in kernel nodes. */
for (i = 0; i < numa_meminfo.nr_blks; i++) {


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