Re: [PATCH v2] mm/memory-failure: fix infinite UCE for VM_PFNMAP'ed page

[Jinjiang Tu <tujinjiang@huawei.com>]

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在 2025/8/14 14:05, jane.chu@oracle.com 写道:
>
> On 8/10/2025 9:33 PM, Jinjiang Tu wrote:
>> When memory_failure() is called for a already hwpoisoned pfn backed with
>> struct page, kill_accessing_process() will conditionally send a 
>> SIGBUS to
>> the current (triggering) process if it maps the page.
>>
>> However, in case the page is not ordinarily mapped, but was mapped 
>> through
>> remap_pfn_range(), kill_accessing_process() wouldn't identify it as 
>> mapped
>> even though hwpoison_pte_range() would be prepared to handle it, because
>> walk_page_range() will skip VM_PFNMAP as default in walk_page_test(). As
>> a result, walk_page_range() will return 0, assuming "not mapped" and 
>> SIGBUS
>> will be skipped. The user task will trigger UCE infinitely because it 
>> will
>> not receive a SIGBUS on access and simply retry.
>>
>> Before commit aaf99ac2ceb7 ("mm/hwpoison: do not send SIGBUS to 
>> processes
>> with recovered clean pages"), kill_accessing_process() will return 
>> EFAULT.
>> For x86, the current task will be killed in kill_me_maybe().
>>
>> To fix it, add .test_walk callback for hwpoison_walk_ops to process
>> VM_PFNMAP VMAs too.
>>
>> Fixes: aaf99ac2ceb7 ("mm/hwpoison: do not send SIGBUS to processes 
>> with recovered clean pages")
>> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
>> ---
>> Changelog since v1:
>>   * update patch description, suggested by David Hildenbrand
>>
>>   mm/memory-failure.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index e2e685b971bb..fa6a8f2cdebc 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -853,9 +853,16 @@ static int hwpoison_hugetlb_range(pte_t *ptep, 
>> unsigned long hmask,
>>   #define hwpoison_hugetlb_range    NULL
>>   #endif
>>   +static int hwpoison_test_walk(unsigned long start, unsigned long end,
>> +                 struct mm_walk *walk)
>> +{
>> +    return 0;
>> +}
>> +
>>   static const struct mm_walk_ops hwpoison_walk_ops = {
>>       .pmd_entry = hwpoison_pte_range,
>>       .hugetlb_entry = hwpoison_hugetlb_range,
>> +    .test_walk = hwpoison_test_walk,
>>       .walk_lock = PGWALK_RDLOCK,
>>   };
>
> Looks good.  Could you add this to stable ?

Yes, I will.

>
> Reviewed-by: Jane Chu <jane.chu@oracle.com>
>
> thanks,
> -jane
>
>
>

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