+ mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix-2.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: secretmem/gup: don't check if page is secretmem without reference
has been added to the -mm tree.  Its filename is
     mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix-2.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix-2.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix-2.patch

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------------------------------------------------------
From: Mike Rapoport <rppt@linux.ibm.com>
Subject: secretmem/gup: don't check if page is secretmem without reference

The check in gup_pte_range() whether a page belongs to a secretmem mapping
is performed before grabbing the page reference.

To avoid potential race move the check after try_grab_compound_head().

Link: https://lkml.kernel.org/r/20210420150049.14031-2-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/mm/gup.c~mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix-2
+++ a/mm/gup.c
@@ -2080,13 +2080,15 @@ static int gup_pte_range(pmd_t pmd, unsi
 		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 		page = pte_page(pte);
 
-		if (page_is_secretmem(page))
-			goto pte_unmap;
-
 		head = try_grab_compound_head(page, 1, flags);
 		if (!head)
 			goto pte_unmap;
 
+		if (unlikely(page_is_secretmem(page))) {
+			put_compound_head(head, 1, flags);
+			goto pte_unmap;
+		}
+
 		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
 			put_compound_head(head, 1, flags);
 			goto pte_unmap;
_

Patches currently in -mm which might be from rppt@linux.ibm.com are

mm-cma-rename-pf_memalloc_nocma-to-pf_memalloc_pin-fix.patch
mmap-make-mlock_future_check-global.patch
riscv-kconfig-make-direct-map-manipulation-options-depend-on-mmu.patch
set_memory-allow-set_direct_map__noflush-for-multiple-pages.patch
set_memory-allow-querying-whether-set_direct_map_-is-actually-enabled.patch
mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas.patch
mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix.patch
mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix-2.patch
pm-hibernate-disable-when-there-are-active-secretmem-users.patch
arch-mm-wire-up-memfd_secret-system-call-where-relevant.patch
arch-mm-wire-up-memfd_secret-system-call-where-relevant-fix.patch
secretmem-test-add-basic-selftest-for-memfd_secret2.patch
secretmem-test-add-basic-selftest-for-memfd_secret2-fix.patch
secretmem-optimize-page_is_secretmem.patch