+ mm-mlock-clear-vma_locked_mask-over-mmap-callback.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/mlock: clear VMA_LOCKED_MASK over mmap callback
has been added to the -mm mm-unstable branch.  Its filename is
     mm-mlock-clear-vma_locked_mask-over-mmap-callback.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mlock-clear-vma_locked_mask-over-mmap-callback.patch

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

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------------------------------------------------------
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Subject: mm/mlock: clear VMA_LOCKED_MASK over mmap callback
Date: Thu, 17 Sep 2026 17:22:32 +0100

Currently there's a confusing mess around VMA_LOCKED_BIT and
VMA_LOCKONFAULT_BIT.

It is permitted for drivers to set any flags they like, with the VMA
already possessing lock flags.

This results in the absurd situation of a VMA possessing both
VMA_SPECIAL_FLAGS and VMA_LOCKED_MASK flags, which is not permitted.

This has resulted in mlock_vma_folio() having a very silly check for this
scenario to work around it.

There is no need for this - just clear the flags before invoking the hook
and reinstate them afterwards if they are required.

Nothing relies upon this being set during the mmap operation.

mmap_prepare is unaffected by this so requires no fix.

Link: https://lore.kernel.org/20260917-b4-mmap-prepare-vma-flag-sanify-v3-23-4583d8a23bca@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
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Cc: Baoquan He <baoquan.he@linux.dev>
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---

 mm/internal.h |    9 +--------
 mm/vma.c      |   14 ++++++++++++++
 2 files changed, 15 insertions(+), 8 deletions(-)

--- a/mm/internal.h~mm-mlock-clear-vma_locked_mask-over-mmap-callback
+++ a/mm/internal.h
@@ -971,14 +971,7 @@ void mlock_folio(struct folio *folio);
 static inline void mlock_vma_folio(struct folio *folio,
 				struct vm_area_struct *vma)
 {
-	/*
-	 * The VM_SPECIAL check here serves two purposes.
-	 * 1) VM_IO check prevents migration from double-counting during mlock.
-	 * 2) Although mmap_region() and mlock_fixup() take care that VM_LOCKED
-	 *    is never left set on a VM_SPECIAL vma, there is an interval while
-	 *    file->f_op->mmap() is using vm_insert_page(s), when VM_LOCKED may
-	 *    still be set while VM_SPECIAL bits are added: so ignore it then.
-	 */
+	/* The VM_IO check prevents migration from double-counting during mlock. */
 	if (unlikely((vma->vm_flags & (VM_LOCKED|VM_SPECIAL)) == VM_LOCKED))
 		mlock_folio(folio);
 }
--- a/mm/vma.c~mm-mlock-clear-vma_locked_mask-over-mmap-callback
+++ a/mm/vma.c
@@ -2607,6 +2607,11 @@ static int __mmap_new_file_vma(struct mm
 	if (!map->vm_file->f_op->mmap)
 		return 0;
 
+	/*
+	 * Driver-specified flags may make the lock flags invalid, so clear
+	 * VMA_LOCKED_MASK and reinstate it afterwards if appropriate.
+	 */
+	vma_clear_flags_mask(vma, VMA_LOCKED_MASK);
 	error = mmap_file(vma->vm_file, vma);
 	map->vm_file = vma->vm_file;
 
@@ -2623,6 +2628,15 @@ static int __mmap_new_file_vma(struct mm
 		return error;
 	}
 
+	/* If VMA flags still valid for locked mask, reinstate. */
+	if (vma_supports_mlock(vma)) {
+		const vma_flags_t mask =
+			vma_flags_and_mask(&map->vma_flags,
+					   VMA_LOCKED_MASK);
+
+		vma_set_flags_mask(vma, mask);
+	}
+
 	map->vma_flags = vma->flags;
 
 	return 0;
_

Patches currently in -mm which might be from ljs@kernel.org are

mm-vmpressure-remove-window-size-todo.patch
tools-testing-selftests-mm-add-missing-gitignore-entries.patch
mm-move-drivers-char-memc-to-mm-char-memc.patch
mm-implement-file_is_dev_zero-to-uniquely-identify-dev-zero.patch
mm-vma-only-permit-map_private-dev-zero-to-be-mapped-anonymous.patch
mm-vma-make-map_private-mapped-dev-zero-mappings-truly-anonymous.patch
tools-testing-vma-add-test-to-assert-map_private-dev-zero-is-anon.patch
tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch
mm-madvise-swap-in-cowd-map_private-file-mappings-on-madv_willneed.patch
mm-huge_memory-zap-deposited-page-tables-after-an-rcu-grace-period.patch
mm-enable-mmu_gather_rcu_table_free-for-most-2-level-architectures.patch
mm-enable-mmu_gather_rcu_table_free-for-mmu-riscv.patch
mm-enable-mmu_gather_rcu_table_free-for-mmu-arm.patch
mm-enable-mmu_gather_rcu_table_free-for-arc-microblaze-xtensa.patch
mm-enable-mmu_gather_rcu_table_free-for-sparc64.patch
mm-enable-mmu_gather_rcu_table_free-for-m68k-coldfire.patch
mm-enable-mmu_gather_rcu_table_free-for-sh-x2.patch
mm-enable-mmu_gather_rcu_table_free-for-m68k-motorola.patch
mm-enable-mmu_gather_rcu_table_free-for-sparc32.patch
mm-make-userland-page-table-freeing-rcu-safe.patch
mm-change-the-contract-for-free_pgtables-update-docs.patch
mm-vma-fix-mmap_prepare-file-handling-remove-file_doesnt_need_get.patch
mm-vma-predicate-setting-mmap_prepare-vma-fields-on-new-vma-alloc.patch
mm-vma-introduce-and-use-vma_can_merge.patch
mm-consistently-validate-vma-state-after-mmap-hooks.patch
mm-vma-ensure-mmap_prepare-doesnt-set-actions-on-a-mergeable-vma.patch
mm-make-map_kernel_pages_-internal-and-unexported.patch
mm-vma-tidy-up-map-kernel-pages-enum-values.patch
mm-add-mmap-action-for-discontiguous-kernel-page-mapping.patch
docs-filesystems-update-mmap_prepare-docs-for-discontig-kernel-pgs.patch
drivers-usb-mon-update-to-use-mmap_prepare-map-kernel-pages.patch
infiniband-update-hfi1-to-use-remap_vmalloc_range.patch
selinux-reject-writable-opens-of-policy-file-drop-mmap-shared-write-check.patch
alsa-pcm-use-vm_insert_page-to-map-pcm-status-page.patch
bpf-arena-mark-arena_map_mmap-mappings-vm_mixedmap.patch
mm-vma-add-vma_is_kernel_owned-predicates.patch
mm-vma-only-allow-mmap-to-clear-vma_maywrite_bit-if-kernel-owned.patch
mm-vma-add-and-use-vma__is_fixed_mapping.patch
scsi-sg-convert-mmap-hook-to-mmap_prepare-and-rework.patch
fbdev-defio-assert-fbinfo_virtfb-drop-vm_io-add-vm_mixedmap.patch
hsi-cmt_speech-convert-mmap-hook-to-mmap_prepare-refactor.patch
mm-gup-error-out-early-on-vma_mayread_bit-vmas.patch
uprobes-remove-vm_io-set-vm_mixedmap-for-mapped-kernel-pages.patch
mm-mlock-clear-vma_locked_mask-over-mmap-callback.patch
mm-mlock-eliminate-weird-vma_io_bit-abuse-and-simplify.patch
mm-vma-enforce-that-only-kernel-owned-mappings-may-set-vma_io_bit.patch
mm-remove-vma_io_bit-check-in-vma_is_kernel_owned.patch
mm-remove-hugetlb_inlineh.patch
mm-rename-is_vm_hugetlb_page-to-vma_is_hugetlb.patch
mm-drop-some-redundant-checks-around-hugetlb-vmas.patch
mm-madvise-update-is_valid_guard_vma-to-use-vma_can_merge.patch
mm-vma-introduce-vma_is_persistent.patch
mm-uffd-use-predicates-for-userfaultfd-checks.patch
mm-madvise-use-predicates-for-madvise-madv_dofork.patch
mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested.patch
mm-eliminate-vma_special_flags-check-in-lru_gen_look_around.patch
mm-avoid-use-of-vma_special_flags-in-migrate_vma_setup.patch
mm-eliminate-vm_special-vma_special_flags.patch
fuse-dax-do-not-set-vm_mixedmap.patch
mm-huge_memory-remove-vma_is_special_huge.patch
mm-vma-introduce-and-use-vma_can_gup.patch
mm-vma-const-ify-vma_assert_stabilised-and-associated-functions.patch
mm-implement-and-use-vma_has_anon_rmap-silence-kcsan.patch
mm-update-comments-to-refer-to-anon-rmap-rather-than-anon_vma.patch