Re: [PATCH] mm: memory-failure: fix potential page refcnt leak in memory_failure()

[Miaohe Lin]

On 2023/7/3 14:37, Naoya Horiguchi wrote:
> On Sat, Jul 01, 2023 at 03:28:37PM +0800, Miaohe Lin wrote:
>> put_ref_page() is not called to drop extra refcnt when comes from madvise
>> in the case pfn is valid but pgmap is NULL leading to page refcnt leak.
> 
> Is this test scenario realistic one?  I don't think that we can call madvise() for
> such a device memory page.  If this is the case, this issue can be thought as
> potentioal one (so no need to send to stable). 

This is a theoretical problem. If pagemap can ever be NULL after page refcnt is increased, this
would occur. I think it's not needed to send to stable too.

> 
>>
>> Fixes: 1e8aaedb182d ("mm,memory_failure: always pin the page in madvise_inject_error")
>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> 
> Anyway, the patch looks good to me. Thanks you.
> 
> Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>

Thanks for your review and comment.