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Date: Tue, 07 Apr 2015 07:15:45 -0700 (PDT)
From: Yasuaki Ishimatsu <yasu.isimatu@gmail.com>
To: Dave Young <dyoung@redhat.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de,
        bhe@redhat.com, mingo@redhat.com, hpa@zytor.com,
        akpm@linux-foundation.org
Subject: Re: [PATCH] x86/numa: kernel stack corruption fix
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Hi Dave,

On Tue, 7 Apr 2015 11:33:55 +0800
Dave Young <dyoung@redhat.com> wrote:

> On 04/06/15 at 07:26am, Yasuaki Ishimatsu wrote:
> > Hi,
> > 
> > On Fri, 3 Apr 2015 15:15:13 +0800
> > Dave Young <dyoung@redhat.com> wrote:
> > 
> > > Hi,
> > > 
> > > On 04/02/15 at 12:36pm, Yasuaki Ishimatsu wrote:
> > > > 
> > > > On Wed, 1 Apr 2015 12:53:46 +0800
> > > > Dave Young <dyoung@redhat.com> 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@redhat.com>
> > > > > ---
> > > > 
> > > > Looks good to me.
> > > > 
> > > > Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> > > 
> > 
> > > Per suggestion from Xishi Qiu, I would like to add below comment in code and repost
> > > Could I carry with your Reviewed-by line? 
> > > 
> > > /* In case booting with numa=off and only using part of system ram
> > >  * ie. mem=nn[kMG] or in kdump kernel, numa_meminfo may not include all the
> > >  * memblock.reserved memory because trim_snb_memory() reserves specific pages 
> > >  * for Sandy Bridge graphics. */
> > 
> > I don't think the issue is related to numa=off. If we use numa=off,
> > all memory ranges which are informed by e820 are managed to Node 0.
> > 
> > The issue occurs when reserved memory ranges are not included
> > in system ram which informed by e820.
> 
> Maybe in theory it is possible that it occurs without numa=off so that numa
> meminfo does not include some reserved regions, but I think I can only
> reproduce it with numa=off.
> 
> But ok, I can use the comment below instead:
> 

> /*
>  * In case booting with mem=nn[kMG] or in kdump kernel, numa_meminfo may not
>  * include all the memblock.reserved memory ranges because trim_snb_memory()
>  * reserves specific pages for Sandy Bridge graphics.
>  */

Looks good to me.

Feel free to add my reviewed by.

Thanks,
Yasuaki Ishimatsu

> 
> Thanks
> Dave