[PATCH 6.19 278/342] mm/mseal: update VMA end correctly on merge

Greg Kroah-Hartman
2026-03-31T16:43:13Z

From: Lorenzo Stoakes (Oracle) <ljs@kernel.org>

commit 2697dd8ae721db4f6a53d4f4cbd438212a80f8dc upstream.

Previously we stored the end of the current VMA in curr_end, and then upon
iterating to the next VMA updated curr_start to curr_end to advance to the
next VMA.

However, this doesn't take into account the fact that a VMA might be
updated due to a merge by vma_modify_flags(), which can result in curr_end
being stale and thus, upon setting curr_start to curr_end, ending up with
an incorrect curr_start on the next iteration.

Resolve the issue by setting curr_end to vma->vm_end unconditionally to
ensure this value remains updated should this occur.

While we're here, eliminate this entire class of bug by simply setting
const curr_[start/end] to be clamped to the input range and VMAs, which
also happens to simplify the logic.

Link: https://lkml.kernel.org/r/20260327173104.322405-1-ljs@kernel.org
Fixes: 6c2da14ae1e0 ("mm/mseal: rework mseal apply logic")
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reported-by: Antonius <antonius@bluedragonsec.com>
Closes: https://lore.kernel.org/linux-mm/CAK8a0jwWGj9-SgFk0yKFh7i8jMkwKm5b0ao9=kmXWjO54veX2g@mail.gmail.com/
Suggested-by: David Hildenbrand (ARM) <david@kernel.org>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/mseal.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/mm/mseal.c
+++ b/mm/mseal.c
@@ -56,7 +56,6 @@ static int mseal_apply(struct mm_struct
unsigned long start, unsigned long end)
{
struct vm_area_struct *vma, *prev;
- unsigned long curr_start = start;
VMA_ITERATOR(vmi, mm, start);

/* We know there are no gaps so this will be non-NULL. */
@@ -66,6 +65,7 @@ static int mseal_apply(struct mm_struct
prev = vma;

for_each_vma_range(vmi, vma, end) {
+ const unsigned long curr_start = MAX(vma->vm_start, start);
const unsigned long curr_end = MIN(vma->vm_end, end);

if (!(vma->vm_flags & VM_SEALED)) {
@@ -79,7 +79,6 @@ static int mseal_apply(struct mm_struct
}

prev = vma;
- curr_start = curr_end;
}

return 0;