Re: [merged mm-hotfixes-stable] mm-secretmem-fix-gup-fast-succeeding-on-secretmem-folios.patch removed from -mm tree

[David Hildenbrand <david@redhat.com>]

On 26.03.24 19:08, Andrew Morton wrote:
> 
> The quilt patch titled
>       Subject: mm/secretmem: fix GUP-fast succeeding on secretmem folios
> has been removed from the -mm tree.  Its filename was
>       mm-secretmem-fix-gup-fast-succeeding-on-secretmem-folios.patch
> 
> This patch was dropped because it was merged into the mm-hotfixes-stable branch
> of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> 

I sent an updated patch that removes the LRU check completely. Still 
time to fix that? :)

> ------------------------------------------------------
> From: David Hildenbrand <david@redhat.com>
> Subject: mm/secretmem: fix GUP-fast succeeding on secretmem folios
> Date: Mon, 25 Mar 2024 14:41:12 +0100
> 
> folio_is_secretmem() states that secretmem folios cannot be LRU folios: so
> we may only exit early if we find an LRU folio.  Yet, we exit early if we
> find a folio that is not a secretmem folio.
> 
> Consequently, folio_is_secretmem() fails to detect secretmem folios and,
> therefore, we can succeed in grabbing a secretmem folio during GUP-fast,
> crashing the kernel when we later try reading/writing to the folio,
> because the folio has been unmapped from the directmap.
> 
> Link: https://lkml.kernel.org/r/20240325134114.257544-2-david@redhat.com
> Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas")
> Signed-off-by: David Hildenbrand <david@redhat.com>
> Reported-by: xingwei lee <xrivendell7@gmail.com>
> Reported-by: yue sun <samsun1006219@gmail.com>
> Closes: https://lore.kernel.org/lkml/CABOYnLyevJeravW=QrH0JUPYEcDN160aZFb7kwndm-J2rmz0HQ@mail.gmail.com/
> Debugged-by: Miklos Szeredi <miklos@szeredi.hu>
> Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
> Tested-by: Miklos Szeredi <mszeredi@redhat.com>
> Cc: Lorenzo Stoakes <lstoakes@gmail.com>
> Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>   include/linux/secretmem.h |    2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/include/linux/secretmem.h~mm-secretmem-fix-gup-fast-succeeding-on-secretmem-folios
> +++ a/include/linux/secretmem.h
> @@ -16,7 +16,7 @@ static inline bool folio_is_secretmem(st
>   	 * We know that secretmem pages are not compound and LRU so we can
>   	 * save a couple of cycles here.
>   	 */
> -	if (folio_test_large(folio) || !folio_test_lru(folio))
> +	if (folio_test_large(folio) || folio_test_lru(folio))
>   		return false;
>   
>   	mapping = (struct address_space *)
> _
> 
> Patches currently in -mm which might be from david@redhat.com are
> 
> mm-madvise-make-madv_populate_readwrite-handle-vm_fault_retry-properly.patch
> mm-madvise-dont-perform-madvise-vma-walk-for-madv_populate_readwrite.patch
> mm-userfaultfd-dont-place-zeropages-when-zeropages-are-disallowed.patch
> s390-mm-re-enable-the-shared-zeropage-for-pv-and-skeys-kvm-guests.patch
> mm-convert-folio_estimated_sharers-to-folio_likely_mapped_shared.patch
> mm-convert-folio_estimated_sharers-to-folio_likely_mapped_shared-fix.patch
> selftests-memfd_secret-add-vmsplice-test.patch
> mm-merge-folio_is_secretmem-into-folio_fast_pin_allowed.patch
> 

-- 
Cheers,

David / dhildenb