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Date:	Thu, 2 Apr 2015 09:51:10 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Dave Young <dyoung@...hat.com>
CC:	<x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<tglx@...utronix.de>, <bhe@...hat.com>, <mingo@...hat.com>,
	<hpa@...or.com>, <akpm@...ux-foundation.org>,
	Tang Chen <tangchen@...fujitsu.com>
Subject: Re: [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. 
>>
>> Fixing this by adding a check, do not call node_set in case nid is MAX_NUMNODES.
>>
>> Signed-off-by: Dave Young <dyoung@...hat.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);

Hi Dave,

How about add some comment here? if set numa=off, numa_meminfo may not include
all the memblock.reserved memory. e.g. trim_snb_memory()

Thanks,
Xishi Qiu

>> +		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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