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. 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> Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas") Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> --- include/linux/secretmem.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h index 35f3a4a8ceb1..6996f1f53f14 100644 --- a/include/linux/secretmem.h +++ b/include/linux/secretmem.h @@ -16,7 +16,7 @@ static inline bool folio_is_secretmem(struct folio *folio) * 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 *) -- 2.43.2
