[merged mm-stable] mm-madvise-update-is_valid_guard_vma-to-use-vma_is_mm_backed.patch removed from -mm tree

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

The quilt patch titled
     Subject: mm/madvise: update is_valid_guard_vma() to use vma_is_mm_backed()
has been removed from the -mm tree.  Its filename was
     mm-madvise-update-is_valid_guard_vma-to-use-vma_is_mm_backed.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Subject: mm/madvise: update is_valid_guard_vma() to use vma_is_mm_backed()
Date: Tue, 13 Oct 2026 16:05:11 +0100

We currently disallow the installation of lightweight guard regions in VMAs
whose flags intersect VMA_SPECIAL_FLAGS or VMA_HUGETLB_BIT, or
VMA_LOCKED_BIT unless allow_locked is set.

hugetlb VMAs set VMA_DONTEXPAND_BIT so this was already redundant,
VMA_SPECIAL_FLAGS already sufficed.

However, now that VMA_IO_BIT is only set if VMA_PFNMAP or VMA_MIXEDMAP_BIT
is set, this check collapses to being the equivalent of
!vma_is_mm_backed(), excluding hugetlb mappings in which guard markers
cannot be installed.

Update is_valid_guard_vma() to reflect this.

No functional change intended.

Link: https://lore.kernel.org/20261013-b4-mmap-prepare-vma-flag-sanify-v6-31-1aa3c9b139f9@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: Jaroslav Kysela <perex@perex.cz>
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Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
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Cc: Xu Xin <xu.xin@linux.dev>
Cc: Ihor Solodrai <ihor.solodrai@linux.dev>
Cc: Bert Karwatzki <spasswolf@web.de>
---

 mm/madvise.c |   20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

--- a/mm/madvise.c~mm-madvise-update-is_valid_guard_vma-to-use-vma_is_mm_backed
+++ a/mm/madvise.c
@@ -1057,19 +1057,25 @@ static long madvise_remove(struct madvis
 	return error;
 }
 
-static bool is_valid_guard_vma(struct vm_area_struct *vma, bool allow_locked)
+static bool is_valid_guard_vma(const struct vm_area_struct *vma,
+			       bool allow_locked)
 {
-	vm_flags_t disallowed = VM_SPECIAL | VM_HUGETLB;
-
 	/*
-	 * A user could lock after setting a guard range but that's fine, as
+	 * A user could lock after setting a guard range but that's fine as
 	 * they'd not be able to fault in. The issue arises when we try to zap
 	 * existing locked VMAs. We don't want to do that.
 	 */
-	if (!allow_locked)
-		disallowed |= VM_LOCKED;
+	if (!allow_locked && vma_test(vma, VMA_LOCKED_BIT))
+		return false;
+	/*
+	 * Guard regions require a VMA whose page tables are managed solely by
+	 * core mm, so the VMA must be mm-backed (excluding hugetlb, in which
+	 * guard markers cannot be installed).
+	 */
+	if (!vma_is_mm_backed(vma) || vma_is_hugetlb(vma))
+		return false;
 
-	return !(vma->vm_flags & disallowed);
+	return true;
 }
 
 static bool is_guard_pte_marker(pte_t ptent)
_

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

mm-vma-fix-expansion-of-vma_mixedmap_bit-vmas.patch
mm-do-not-unintentionally-overwrite-atomic-vma-flags.patch
mm-vma-avoid-losing-atomic-vma-flags-when-setting-sticky-vma-flags.patch