dasmon_test_filter_out() test checks if damos_filter_match() of an address filter splits the region as expected under a given condition. But, the test continued regardless of the split successes. As a result, the later part of the test could dereference invalid pointers that returned from damon_next_region(). Further, it could corrupt memory from damon_destroy_region(). The consequent user impact (memory corruption) is quite bad. The realistic user impact would be limited, though. It would affect only test run setups. Fix it by exiting early for the number of regions test failure. The issue was discovered [1] by Sashiko. [1] https://lore.kernel.org/20260714142352.100478-1-sj@kernel.org Fixes: 26713c890875 ("mm/damon/core-test: add a unit test for __damos_filter_out()") Cc: # 6.6.x Signed-off-by: SJ Park --- mm/damon/tests/core-kunit.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h index 322a295ac2cec..eddf3a0484583 100644 --- a/mm/damon/tests/core-kunit.h +++ b/mm/damon/tests/core-kunit.h @@ -1365,6 +1365,8 @@ static void damos_test_filter_out(struct kunit *test) KUNIT_EXPECT_EQ(test, r->ar.start, 1); KUNIT_EXPECT_EQ(test, r->ar.end, 2); KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 2); + if (damon_nr_regions(t) != 2) + goto out; r2 = damon_next_region(r); KUNIT_EXPECT_EQ(test, r2->ar.start, 2); KUNIT_EXPECT_EQ(test, r2->ar.end, 4); @@ -1379,11 +1381,14 @@ static void damos_test_filter_out(struct kunit *test) KUNIT_EXPECT_EQ(test, r->ar.start, 2); KUNIT_EXPECT_EQ(test, r->ar.end, 6); KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 2); + if (damon_nr_regions(t) != 2) + goto out; r2 = damon_next_region(r); KUNIT_EXPECT_EQ(test, r2->ar.start, 6); KUNIT_EXPECT_EQ(test, r2->ar.end, 8); damon_destroy_region(r2, t); +out: damon_free_target(t); damos_free_filter(f); } -- 2.47.3