[merged mm-stable] mm-damon-vaddr-kunit-check-region-count-in-three_regions-test.patch removed from -mm tree

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

The quilt patch titled
     Subject: mm/damon/vaddr-kunit: check region count in three_regions test
has been removed from the -mm tree.  Its filename was
     mm-damon-vaddr-kunit-check-region-count-in-three_regions-test.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: SJ Park <sj@kernel.org>
Subject: mm/damon/vaddr-kunit: check region count in three_regions test
Date: Fri, 17 Jul 2026 17:14:37 -0700

damon_do_test_apply_three_regions() iterates regions after
damon_set_regions() call assuming the function would succeed at setting
the number of regions the same to the expected one.  It might have failed.
In this case, __nth_region_of() in the iteration could return NULL and
NULL dereference can happen in the test.

The consequent user impact (NULL dereference) is quite bad.  The realistic
user impact would be limited, though.  It would affect only test run
setups.

Fix it by testing if the number of regions was also changed as expected
and exit early for the failure.

The issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/20260718001442.87129-4-sj@kernel.org
Link: https://lore.kernel.org/20260713144757.39740-1-sj@kernel.org [1]
Fixes: 17ccae8bb5c9 ("mm/damon: add kunit tests")
Signed-off-by: SJ Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: <stable@vger.kernel.org> # 5.15.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/tests/vaddr-kunit.h |    5 +++++
 1 file changed, 5 insertions(+)

--- a/mm/damon/tests/vaddr-kunit.h~mm-damon-vaddr-kunit-check-region-count-in-three_regions-test
+++ a/mm/damon/tests/vaddr-kunit.h
@@ -158,12 +158,17 @@ static void damon_do_test_apply_three_re
 		kunit_skip(test, "second damon_set_regions() fail");
 	}
 
+	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), nr_expected / 2);
+	if (damon_nr_regions(t) != nr_expected / 2)
+		goto out;
+
 	for (i = 0; i < nr_expected / 2; i++) {
 		r = __nth_region_of(t, i);
 		KUNIT_EXPECT_EQ(test, r->ar.start, expected[i * 2]);
 		KUNIT_EXPECT_EQ(test, r->ar.end, expected[i * 2 + 1]);
 	}
 
+out:
 	damon_destroy_target(t, NULL);
 }
 
_

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