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SubjectRe: [PATCH] x86/numa: kernel stack corruption fix
On 2015/4/1 13:11, Dave Young wrote:

> Ccing Xishi Qiu who wrote the clear_kernel_node_hotplug code.
>
> On 04/01/15 at 12:53pm, Dave Young wrote:
>> 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.
>>

Hi Dave,

Is it means, first reserved region 0x40000000 - 0x40100000, then boot the kdump
kernel, so this region is not include in "numa_meminfo", and memblock.reserved
(0x40004000) is still MAX_NUMNODES from trim_snb_memory().

numa_clear_kernel_node_hotplug
{
...
for (i = 0; i < numa_meminfo.nr_blks; i++) {
struct numa_memblk *mb = &numa_meminfo.blk[i];

memblock_set_node(mb->start, mb->end - mb->start,
&memblock.reserved, mb->nid); // this will not reset 0x40004000's node, right?
}
...
}

Thanks
Xishi Qiu

>> 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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