Re: [PATCH 6.6.y] mm/hugetlb: fix potential race in __update_and_free_hugetlb_folio()

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Aug 07, 2024 at 11:58:53AM +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 the 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.
> 
> Link: https://lkml.kernel.org/r/20240708025127.107713-1-linmiaohe@huawei.com
> Fixes: 32c877191e02 ("hugetlb: do not clear hugetlb dtor until allocating vmemmap")
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> Acked-by: Muchun Song <muchun.song@linux.dev>
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> (cherry picked from commit 5596d9e8b553dacb0ac34bcf873cbbfb16c3ba3e)
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>  mm/hugetlb.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 

Backports now queued up, thanks.

greg k-h