+ mm-mremap-catch-invalid-multi-vma-moves-earlier-fix.patch added to mm-hotfixes-unstable branch

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

The patch titled
     Subject: mm/mremap: do not incorrectly reference invalid VMA in VM_WARN_ON_ONCE()
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-mremap-catch-invalid-multi-vma-moves-earlier-fix.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mremap-catch-invalid-multi-vma-moves-earlier-fix.patch

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

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------------------------------------------------------
From: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Subject: mm/mremap: do not incorrectly reference invalid VMA in VM_WARN_ON_ONCE()
Date: Sat, 16 Aug 2025 08:37:41 +0100

The VMA which is referenced here may have since been merged (which is the
entire point of the warning), and yet we still reference it.

Fix this by storing whether or not a multi move is permitted ahead of time
and have the VM_WARN_ON_ONCE() be predicated on this.

Link: https://lkml.kernel.org/r/b6dbda20-667e-4053-abae-8ed4fa84bb6c@lucifer.local
Reported-by: syzbot+4e221abf50259362f4f4@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-mm/689ff5f6.050a0220.e29e5.0030.GAE@google.com/
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mremap.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/mm/mremap.c~mm-mremap-catch-invalid-multi-vma-moves-earlier-fix
+++ a/mm/mremap.c
@@ -1837,6 +1837,7 @@ static unsigned long remap_move(struct v
 		unsigned long addr = max(vma->vm_start, start);
 		unsigned long len = min(end, vma->vm_end) - addr;
 		unsigned long offset, res_vma;
+		bool multi_allowed;
 
 		/* No gap permitted at the start of the range. */
 		if (!seen_vma && start < vma->vm_start)
@@ -1865,7 +1866,8 @@ static unsigned long remap_move(struct v
 		vrm->new_addr = target_addr + offset;
 		vrm->old_len = vrm->new_len = len;
 
-		if (!vma_multi_allowed(vma)) {
+		multi_allowed = vma_multi_allowed(vma);
+		if (!multi_allowed) {
 			/* This is not the first VMA, abort immediately. */
 			if (seen_vma)
 				return -EFAULT;
@@ -1881,8 +1883,7 @@ static unsigned long remap_move(struct v
 			return res_vma;
 
 		if (!seen_vma) {
-			VM_WARN_ON_ONCE(vma_multi_allowed(vma) &&
-					res_vma != new_addr);
+			VM_WARN_ON_ONCE(multi_allowed && res_vma != new_addr);
 			res = res_vma;
 		}
 
_

Patches currently in -mm which might be from lorenzo.stoakes@oracle.com are

tools-testing-add-linux-argsh-header-and-fix-radix-vma-tests.patch
mm-mremap-allow-multi-vma-move-when-filesystem-uses-thp_get_unmapped_area.patch
mm-mremap-catch-invalid-multi-vma-moves-earlier.patch
mm-mremap-catch-invalid-multi-vma-moves-earlier-fix.patch
selftests-mm-add-test-for-invalid-multi-vma-operations.patch
mm-add-bitmap-mm-flags-field.patch
mm-add-bitmap-mm-flags-field-fix.patch
mm-convert-core-mm-to-mm_flags_-accessors.patch
mm-convert-prctl-to-mm_flags_-accessors.patch
mm-convert-arch-specific-code-to-mm_flags_-accessors.patch
mm-convert-arch-specific-code-to-mm_flags_-accessors-fix.patch
mm-convert-uprobes-to-mm_flags_-accessors.patch
mm-update-coredump-logic-to-correctly-use-bitmap-mm-flags.patch
mm-correct-sign-extension-issue-in-mmf_-flag-masks.patch
mm-update-fork-mm-flags-initialisation-to-use-bitmap.patch
mm-convert-remaining-users-to-mm_flags_-accessors.patch
mm-replace-mm-flags-with-bitmap-entirely-and-set-to-64-bits.patch