Message-ID: <0f0a190a-9a69-dbfe-6964-a0574cb5fc8d@huawei.com>
Date: Thu, 28 Aug 2025 10:53:38 +0800
From: Miaohe Lin <linmiaohe@...wei.com>
To: David Hildenbrand <david@...hat.com>, <akpm@...ux-foundation.org>
CC: <nao.horiguchi@...il.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] mm/memory-failure: fix
 VM_BUG_ON_PAGE(PagePoisoned(page)) when unpoison memory

On 2025/8/26 18:58, David Hildenbrand wrote:
> On 26.08.25 09:57, Miaohe Lin wrote:
>> When I did memory failure tests, below panic occurs:
>>
>> page dumped because: VM_BUG_ON_PAGE(PagePoisoned(page))
>> kernel BUG at include/linux/page-flags.h:616!
>> Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
>> CPU: 3 PID: 720 Comm: bash Not tainted 6.10.0-rc1-00195-g148743902568 #40
>> RIP: 0010:unpoison_memory+0x2f3/0x590
>> RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
>> RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
>> RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
>> RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
>> R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
>> R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
>> FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
>> Call Trace:
>>   <TASK>
>>   unpoison_memory+0x2f3/0x590
>>   simple_attr_write_xsigned.constprop.0.isra.0+0xb3/0x110
>>   debugfs_attr_write+0x42/0x60
>>   full_proxy_write+0x5b/0x80
>>   vfs_write+0xd5/0x540
>>   ksys_write+0x64/0xe0
>>   do_syscall_64+0xb9/0x1d0
>>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> RIP: 0033:0x7f08f0314887
>> RSP: 002b:00007ffece710078 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
>> RAX: ffffffffffffffda RBX: 0000000000000009 RCX: 00007f08f0314887
>> RDX: 0000000000000009 RSI: 0000564787a30410 RDI: 0000000000000001
>> RBP: 0000564787a30410 R08: 000000000000fefe R09: 000000007fffffff
>> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000009
>> R13: 00007f08f041b780 R14: 00007f08f0417600 R15: 00007f08f0416a00
>>   </TASK>
>> Modules linked in: hwpoison_inject
>> ---[ end trace 0000000000000000 ]---
>> RIP: 0010:unpoison_memory+0x2f3/0x590
>> RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
>> RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
>> RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
>> RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
>> R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
>> R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
>> FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
>> Kernel panic - not syncing: Fatal exception
>> Kernel Offset: 0x31c00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
>> ---[ end Kernel panic - not syncing: Fatal exception ]---
>>
>> The root cause is that unpoison_memory() tries to check the PG_HWPoison
>> flags of an uninitialized page. So VM_BUG_ON_PAGE(PagePoisoned(page)) is
>> triggered. This can be reproduced by below steps:
>> 1.Offline memory block:
>>   echo offline > /sys/devices/system/memory/memory12/state
>> 2.Get offlined memory pfn:
>>   page-types -b n -rlN
>> 3.Write pfn to unpoison-pfn
>>   echo <pfn> > /sys/kernel/debug/hwpoison/unpoison-pfn
>>
>> This scene can be identified by pfn_to_online_page() returning NULL.
>> And ZONE_DEVICE pages are never expected, so we can simply fail if
>> pfn_to_online_page() == NULL to fix the bug.
>>
>> Suggested-by: David Hildenbrand <david@...hat.com>
>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> 
> Similar to
> 
> commit 96c804a6ae8c59a9092b3d5dd581198472063184
> Author: David Hildenbrand <david@...hat.com>
> Date:   Fri Oct 18 20:19:23 2019 -0700
> 
>     mm/memory-failure.c: don't access uninitialized memmaps in memory_failure()
>         We should check for pfn_to_online_page() to not access uninitialized
>     memmaps.  Reshuffle the code so we don't have to duplicate the error
>     message.
>         Link: http://lkml.kernel.org/r/20191009142435.3975-3-david@redhat.com
>     Signed-off-by: David Hildenbrand <david@...hat.com>
>     Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online")      [visible after d0dc12e86b319]
>     Acked-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
>     Cc: Michal Hocko <mhocko@...nel.org>
>     Cc: <stable@...r.kernel.org>    [4.13+]
>     Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
>     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> 
> We should likely just use the exact same Fixes:
> 
> Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online")      [visible after d0dc12e86b319]
> 

Thanks for your information. Will add it in next version.

> 
> Not sure about CCing stable. This is a pure debugging feature (depends on DEBUG_KERNEL),
> and someone really has to trigger it manually to provoke this. So I would not CC stable.
> 
>> ---
>> v2:
>>    Use pfn_to_online_page per David. Thanks.
>> v3:
>>    Simply fail if pfn_to_online_page() == NULL per David. Thanks.
>> ---
>>   mm/memory-failure.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index c15ffee7d32b..212620308028 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -2572,7 +2572,9 @@ int unpoison_memory(unsigned long pfn)
>>       if (!pfn_valid(pfn))
>>           return -ENXIO;
>>   -    p = pfn_to_page(pfn);
>> +    p = pfn_to_online_page(pfn);
>> +    if (!p)
>> +        return -EIO;
> 
> I think we can just drop the pfn_valid() check now. pfn_to_online_page() implies a pfn_valid() check.
> 

Will do.

Thanks.
.

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