Re: [PATCH 6.1.y] mm/damon/core-kunit: check region count before testing in split_at()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The error-checking condition `!damon_nr_regions(t) != 2` is always true due to operator precedence, causing the test to unconditionally skip its core assertions.
--

commit 6fefc501724f8572d4bbc1782d2ab55fa7568e21
Author: SJ Park <sj@kernel.org>

mm/damon/core-kunit: check region count before testing in split_at()

This patch updates damon_test_split_at() to verify the region count was
successfully changed before proceeding. This prevents invalid pointer
dereferences if the split fails.

Link: https://lore.kernel.org/20260718001442.87129-3-sj@kernel.org
Link: https://lore.kernel.org/20260714142352.100478-1-sj@kernel.org [1]

> diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h
> index d8fef225930a5..1dd17d43a642c 100644
> --- a/mm/damon/core-test.h
> +++ b/mm/damon/core-test.h
> @@ -162,6 +162,9 @@ static void damon_test_split_at(struct kunit *test)
>  	}
>  	damon_add_region(r, t);
>  	damon_split_region_at(t, r, 25);
> +	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 2);
> +	if (!damon_nr_regions(t) != 2)
> +		goto out;

[Severity: Medium]
Will this error-checking condition unintentionally skip the core assertions
of the test?

Because of operator precedence, !damon_nr_regions(t) evaluates to either 0
or 1. Neither 0 nor 1 equals 2, meaning the inequality (!= 2) is always true.

This seems to force the test to unconditionally take the goto out path, 
bypassing the boundary validations it is designed to perform.

>  	KUNIT_EXPECT_EQ(test, r->ar.start, 0ul);
>  	KUNIT_EXPECT_EQ(test, r->ar.end, 25ul);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260909035813.162131-1-sj@kernel.org?part=1