Re: [PATCH v5] mm/gup: check page hwposion status for coredump.

David Hildenbrand
2021-03-31T07:06:21Z

On 31.03.21 08:53, HORIGUCHI NAOYA(堀口 直也) wrote:
> On Wed, Mar 31, 2021 at 07:07:39AM +0100, Matthew Wilcox wrote:
>> On Wed, Mar 31, 2021 at 01:52:59AM +0000, HORIGUCHI NAOYA(堀口 直也) wrote:
>>> If we successfully unmapped but failed in truncate_error_page() for example,
>>> the processes mapping the page would get -EFAULT as expected. But even in
>>> this case, other processes could reach the error page via page cache and
>>> __get_user_pages_locked() for them could return the hwpoisoned page.
>>
>> How would that happen? We check PageHWPoison before inserting a page
>> into the page tables. See, eg, filemap_map_pages() and __do_fault().
>
> Ah, you're right, that never happens. I misread the code.
> Thanks for correcting me.
>

I'm wondering if there is a small race window, if we poison a page while
inserting it.

--
Thanks,

David / dhildenb