+ mm-madvise-preserve-vma_softdirty_bit-when-changing-anonymous-names.patch added to mm-unstable branch

+ mm-madvise-preserve-vma_softdirty_bit-when-changing-anonymous-names.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/madvise: preserve VMA_SOFTDIRTY_BIT when changing anonymous names
has been added to the -mm mm-unstable branch.  Its filename is
     mm-madvise-preserve-vma_softdirty_bit-when-changing-anonymous-names.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-madvise-preserve-vma_softdirty_bit-when-changing-anonymous-names.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: "David Hildenbrand (Arm)" <david@kernel.org>
Subject: mm/madvise: preserve VMA_SOFTDIRTY_BIT when changing anonymous names
Date: Fri, 23 Oct 2026 14:47:29 +0100

When changing the anonymous VMA name, madvise_update_vma() calls
vma_modify_name() to possibly merge with adjacent VMAs. We don't call
vma_modify_flags() and consequently don't obtain the new VMA flags.

Later in the function we update the VMA flags to the stale new_vma_flags
we obtained before. This can result in us losing the VMA_SOFTDIRTY_BIT
flag set on a VMA we just merged with.

There is no need to update the VMA flags at all, so just exit early. This
skips calling khugepaged_enter_vma(), but since the flags didn't change
this is fine.

[ljs@kernel.org: minor edit of commit message, rebased]
Link: https://lore.kernel.org/20261023-fix-vma-atomic-v1-3-8ff4fae1fc85@kernel.org
Fixes: 9a10064f5625 ("mm: add a field to store names for private anonymous memory")
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Jann Horn <jannh@google.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: SJ Park <sj@kernel.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Colin Cross <ccross@google.com>
Cc: <stable@vger.kernel.org>
---

 mm/madvise.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/madvise.c~mm-madvise-preserve-vma_softdirty_bit-when-changing-anonymous-names
+++ a/mm/madvise.c
@@ -177,6 +177,9 @@ static int madvise_update_vma(vm_flags_t
 
 	/* vm_flags is protected by the mmap_lock held in write mode. */
 	vma_start_write(vma);
+	if (set_new_anon_name)
+		return replace_anon_vma_name(vma, anon_name);
+
 	vma_overwrite_flags(vma, new_vma_flags);
 	/*
 	 * If the vma become good for khugepaged to scan,
@@ -186,9 +189,6 @@ static int madvise_update_vma(vm_flags_t
 	if (vma_flags_test(&new_vma_flags, VMA_HUGEPAGE_BIT))
 		khugepaged_enter_vma(vma, vma_flags_to_legacy(new_vma_flags));
 
-	if (set_new_anon_name)
-		return replace_anon_vma_name(vma, anon_name);
-
 	return 0;
 }
 
_

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

mm-fix-address-wraparound-when-scanning-large-folio-ptes.patch
mm-hugetlb-fix-use-after-free-in-hugetlb_mfill_atomic_pte.patch
mm-hugetlb-tolerate-uffd-bits-set-without-uffd-for-prot_none-ptes.patch
mm-hugetlb-tolerate-uffd_wp-markers-outside-uffd-wp-vmas.patch
mm-mremap-fix-calling-fixup_hugetlb_reservations-on-the-wrong-vma.patch
arm64-mm-move-__check_safe_pte_update-fix.patch
mm-sparse-move-mem_section-init-to-sparse_extreme_init.patch
mm-sparse-refactor-sparse_sections_init.patch
mm-sparse-move-initialization-of-section-metadata-to-sparse_metadata_init.patch
mm-sparse-rename-and-cleanup-sparse_init_nid.patch
mm-sparse-cleanup-sparse_init_one_section.patch
mm-sparse-rename-__highest_present_section_nr-to-__highest_used_section_nr.patch
mm-sparse-remove-pfn_in_present_section.patch
mm-sparse-move-__highest_used_section_nr-handling.patch
scripts-gdb-mmpy-remove-fallbacks-for-section_has_mem_map-and-section_is_early.patch
mm-sparse-remove-section_marked_present.patch
mm-sparse-remove-flags-parameter-from-sparse_init_one_section.patch
fs-proc-page-clarify-comment-in-get_max_dump_pfn.patch
mm-memory_hotplug-drop-config_have_arch_pfn_valid-handling-from-pfn_to_online_page.patch
vmcoreinfo-export-section_has_mem_map.patch
mm-disallow-ioremaping-ordinary-ram-in-generic_access_phys.patch
mm-userfaultfd-only-allocate-anon_vma-in-cow-mappings.patch
mm-hugetlb-disable-pmd-sharing-for-uffd-missing-mode.patch
mm-vma-write-lock-source-vma-before-duplicating-it-in-__split_vma.patch
mm-madvise-preserve-vma_softdirty_bit-when-changing-anonymous-names.patch