On Tue, Jan 27, 2026 at 09:25:51AM +0800, Feng Jiang wrote:
> Add a KUnit test for strlen() to verify correctness across
> different string lengths and memory alignments.
>
> Signed-off-by: Feng Jiang <[email protected]>
> Acked-by: Andy Shevchenko <[email protected]>
> Tested-by: Joel Stanley <[email protected]>
> ---
> lib/tests/string_kunit.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/lib/tests/string_kunit.c b/lib/tests/string_kunit.c
> index f9a8e557ba77..bc5130c6e5e9 100644
> --- a/lib/tests/string_kunit.c
> +++ b/lib/tests/string_kunit.c
> @@ -17,6 +17,9 @@
> #define STRCMP_TEST_EXPECT_LOWER(test, fn, ...) KUNIT_EXPECT_LT(test,
> fn(__VA_ARGS__), 0)
> #define STRCMP_TEST_EXPECT_GREATER(test, fn, ...) KUNIT_EXPECT_GT(test,
> fn(__VA_ARGS__), 0)
>
> +#define STRING_TEST_MAX_LEN 128
> +#define STRING_TEST_MAX_OFFSET 16
> +
> static void string_test_memset16(struct kunit *test)
> {
> unsigned i, j, k;
> @@ -104,6 +107,28 @@ static void string_test_memset64(struct kunit *test)
> }
> }
>
> +static void string_test_strlen(struct kunit *test)
> +{
> + const size_t buf_size = STRING_TEST_MAX_LEN + STRING_TEST_MAX_OFFSET +
> 1;
> + size_t len, offset;
> + char *s;
> +
> + s = kunit_kzalloc(test, buf_size, GFP_KERNEL);
One aspect of "correctness" that we might want to include here is making
sure we don't have any implementations that over-read. To that end,
perhaps this test can put the string at the end of a vmalloc allocation
(so that the end of the string is right up against an unallocated memory
space).
> + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, s);
> +
> + memset(s, 'A', buf_size);
> + s[buf_size - 1] = '\0';
> +
> + for (offset = 0; offset < STRING_TEST_MAX_OFFSET; offset++) {
> + for (len = 0; len <= STRING_TEST_MAX_LEN; len++) {
> + s[offset + len] = '\0';
> + KUNIT_EXPECT_EQ_MSG(test, strlen(s + offset), len,
> + "offset:%zu len:%zu", offset, len);
> + s[offset + len] = 'A';
> + }
> + }
> +}
It would require building the string backwards here. Or maybe we just
need a separate test for the over-read concerns?
Thoughts?
-Kees
--
Kees Cook
