Re: [PATCH] mm/hugetlb: fix potential race in __update_and_free_hugetlb_folio()

[Oscar Salvador]

On Mon, Jul 08, 2024 at 10:51:27AM +0800, Miaohe Lin wrote:
> There is a potential race between __update_and_free_hugetlb_folio() and
> try_memory_failure_hugetlb():
> 
>  CPU1					CPU2
>  __update_and_free_hugetlb_folio	try_memory_failure_hugetlb
> 					 folio_test_hugetlb
> 					  -- It's still hugetlb folio.
>   folio_clear_hugetlb_hwpoison
>   					  spin_lock_irq(&hugetlb_lock);
> 					   __get_huge_page_for_hwpoison
> 					    folio_set_hugetlb_hwpoison
> 					  spin_unlock_irq(&hugetlb_lock);
>   spin_lock_irq(&hugetlb_lock);
>   __folio_clear_hugetlb(folio);
>    -- Hugetlb flag is cleared but too late.
>   spin_unlock_irq(&hugetlb_lock);
> 
> When above race occurs, raw error page info will be leaked. Even worse,
> raw error pages won't have hwpoisoned flag set and hit pcplists/buddy.
> Fix this issue by deferring folio_clear_hugetlb_hwpoison() until
> __folio_clear_hugetlb() is done. So all raw error pages will have
> hwpoisoned flag set.
> 
> Fixes: 32c877191e02 ("hugetlb: do not clear hugetlb dtor until allocating vmemmap")
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>

Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>


-- 
Oscar Salvador
SUSE Labs