+ mm-avoid-using-vma_merge-for-new-vmas-fix.patch added to mm-unstable branch

+ mm-avoid-using-vma_merge-for-new-vmas-fix.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm: only advance iterator if prev exists
has been added to the -mm mm-unstable branch.  Its filename is
     mm-avoid-using-vma_merge-for-new-vmas-fix.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-avoid-using-vma_merge-for-new-vmas-fix.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 <lorenzo.stoakes@oracle.com>
Subject: mm: only advance iterator if prev exists
Date: Tue, 27 Aug 2024 11:59:27 +0100

If we have no VMAs prior to us, such as in a case where we are
mremap()'ing a VMA backwards, then we will advance the iterator backwards
to 0, before moving to the original range again.

The intent is to position the iterator at or before the gap, therefore we
must avoid this - this is simply addressed by only advancing the iterator
should vma_prev() yield a result.

Link: https://lkml.kernel.org/r/c0ef6b6a-1c9b-4da2-a180-c8e1c73b1c28@lucifer.local
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202408271452.c842a71d-lkp@intel.com
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vma.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/vma.c~mm-avoid-using-vma_merge-for-new-vmas-fix
+++ a/mm/vma.c
@@ -1557,8 +1557,8 @@ struct vm_area_struct *copy_vma(struct v
 	vmg.vma = NULL; /* New VMA range. */
 	vmg.pgoff = pgoff;
 	vmg.next = vma_next(&vmi);
-	vma_prev(&vmi);
-	vma_iter_next_range(&vmi);
+	if (vma_prev(&vmi))
+		vma_iter_next_range(&vmi);
 
 	new_vma = vma_merge_new_range(&vmg);
 
_

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

userfaultfd-move-core-vma-manipulation-logic-to-mm-userfaultfdc.patch
userfaultfd-move-core-vma-manipulation-logic-to-mm-userfaultfdc-fix.patch
mm-move-vma_modify-and-helpers-to-internal-header.patch
mm-move-vma_shrink-vma_expand-to-internal-header.patch
mm-move-internal-core-vma-manipulation-functions-to-own-file.patch
maintainers-add-entry-for-new-vma-files.patch
tools-separate-out-shared-radix-tree-components.patch
tools-add-skeleton-code-for-userland-testing-of-vma-logic.patch
mm-vma-track-start-and-end-for-munmap-in-vma_munmap_struct-fix.patch
tools-improve-vma-test-makefile.patch
tools-add-vma-merge-tests.patch
mm-introduce-vma_merge_struct-and-abstract-vma_mergevma_modify.patch
mm-remove-duplicated-open-coded-vma-policy-check.patch
mm-abstract-vma_expand-to-use-vma_merge_struct.patch
mm-avoid-using-vma_merge-for-new-vmas.patch
mm-avoid-using-vma_merge-for-new-vmas-fix.patch
mm-make-vma_prepare-and-friends-static-and-internal-to-vmac.patch
mm-introduce-commit_merge-abstracting-final-commit-of-merge.patch
mm-refactor-vma_merge-into-modify-only-vma_merge_existing_range.patch
mm-rework-vm_ops-close-handling-on-vma-merge.patch