The patch titled Subject: mm/secretmem: fix GUP-fast succeeding on secretmem folios has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-secretmem-fix-gup-fast-succeeding-on-secretmem-folios.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ 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-J2rm... 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-secretmem-fix-gup-fast-succeeding-on-secretmem-folios.patch 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