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/mm-secretmem-fix-gup-fast-succeeding-on-secretmem-folios.patch
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@xxxxxxxxxx>
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@xxxxxxxxxx
Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas")
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reported-by: xingwei lee <xrivendell7@xxxxxxxxx>
Reported-by: yue sun <samsun1006219@xxxxxxxxx>
Closes: https://lore.kernel.org/lkml/CABOYnLyevJeravW=QrH0JUPYEcDN160aZFb7kwndm-J2rmz0HQ@xxxxxxxxxxxxxx/
Debugged-by: Miklos Szeredi <miklos@xxxxxxxxxx>
Reviewed-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Tested-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: "Mike Rapoport (IBM)" <rppt@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxx 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
