Re: [PATCH v2] mm/memory-failure: fix VM_BUG_ON_PAGE(PagePoisoned(page)) when unpoison memory

[Miaohe Lin <linmiaohe@huawei.com>]

On 2024/12/19 20:18, David Hildenbrand wrote:
> On 19.12.24 12:52, Miaohe Lin wrote:
>> When I did memory failure tests recently, 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
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>> ---
>> v2: Use pfn_to_online_page per David. Thanks.
>> ---
>>   mm/memory-failure.c | 14 +++++++++++---
>>   1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index a7b8ccd29b6f..02be0596ce67 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -2556,10 +2556,18 @@ int unpoison_memory(unsigned long pfn)
>>       static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
>>                       DEFAULT_RATELIMIT_BURST);
>>   -    if (!pfn_valid(pfn))
>> -        return -ENXIO;
>> +    p = pfn_to_online_page(pfn);
>> +    if (!p) {
>> +        struct dev_pagemap *pgmap;
>>   -    p = pfn_to_page(pfn);
>> +        if (!pfn_valid(pfn))
>> +            return -ENXIO;
>> +        pgmap = get_dev_pagemap(pfn, NULL);
>> +        if (!pgmap)
>> +            return -ENXIO;
>> +        put_dev_pagemap(pgmap);
>> +        p = pfn_to_page(pfn);
>> +    }
> 
> Hm, I wonder if we can do anything reasonable with ZONE_DEVICE pages here?

All I can see in unpoison_memory() is folio_test_clear_hwpoison() for ZONE_DEVICE pages.

> 
> CCing Dan, maybe he knows if this interface used to do something reasonable with ZONE_DEVICE pages.
> 
> Also, I'm not sure about using the page after doing the put_dev_pagemap(). Likely we would have to do that at the before exiting from this function.

IMHO, the page can be used after doing put_dev_pagemap(). The page should still be
available while it has HWPoison set. Or are you worrying about memory offline? That
might not be the scope of this problem. But I might be miss something.

Thanks.
.