linux-kernel - [PATCH v3 2/8] lib/string_kunit: add correctness test for strnlen

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Message-Id: <20260120065852.166857-3-jiangfeng@kylinos.cn>
Date: Tue, 20 Jan 2026 14:58:46 +0800
From: Feng Jiang <jiangfeng@...inos.cn>
To: pjw@...nel.org,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	alex@...ti.fr,
	akpm@...ux-foundation.org,
	kees@...nel.org,
	andy@...nel.org,
	jiangfeng@...inos.cn,
	ebiggers@...nel.org,
	martin.petersen@...cle.com,
	ardb@...nel.org,
	charlie@...osinc.com,
	conor.dooley@...rochip.com,
	ajones@...tanamicro.com,
	linus.walleij@...aro.org,
	nathan@...nel.org
Cc: linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	Joel Stanley <joel@....id.au>
Subject: [PATCH v3 2/8] lib/string_kunit: add correctness test for strnlen

Add a KUnit test for strnlen() to verify correctness across
different string lengths and memory alignments.

Suggested-by: Andy Shevchenko <andy@...nel.org>
Tested-by: Joel Stanley <joel@....id.au>
Signed-off-by: Feng Jiang <jiangfeng@...inos.cn>
---
 lib/tests/string_kunit.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/lib/tests/string_kunit.c b/lib/tests/string_kunit.c
index 88da97e50c8e..546cf403317c 100644
--- a/lib/tests/string_kunit.c
+++ b/lib/tests/string_kunit.c
@@ -129,6 +129,38 @@ static void string_test_strlen(struct kunit *test)
 	}
 }
 
+static void string_test_strnlen(struct kunit *test)
+{
+	char *s;
+	size_t len, offset;
+	const size_t buf_size = STRING_TEST_MAX_LEN + STRING_TEST_MAX_OFFSET + 1;
+
+	s = kunit_kzalloc(test, buf_size, GFP_KERNEL);
+	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';
+
+			if (len > 0)
+				KUNIT_EXPECT_EQ(test, strnlen(s + offset, len - 1), len - 1);
+			if (len > 1)
+				KUNIT_EXPECT_EQ(test, strnlen(s + offset, len - 2), len - 2);
+
+			KUNIT_EXPECT_EQ(test, strnlen(s + offset, len), len);
+
+			KUNIT_EXPECT_EQ(test, strnlen(s + offset, len + 1), len);
+			KUNIT_EXPECT_EQ(test, strnlen(s + offset, len + 2), len);
+			KUNIT_EXPECT_EQ(test, strnlen(s + offset, len + 10), len);
+
+			s[offset + len] = 'A';
+		}
+	}
+}
+
 static void string_test_strchr(struct kunit *test)
 {
 	const char *test_string = "abcdefghijkl";
@@ -644,6 +676,7 @@ static struct kunit_case string_test_cases[] = {
 	KUNIT_CASE(string_test_memset32),
 	KUNIT_CASE(string_test_memset64),
 	KUNIT_CASE(string_test_strlen),
+	KUNIT_CASE(string_test_strnlen),
 	KUNIT_CASE(string_test_strchr),
 	KUNIT_CASE(string_test_strnchr),
 	KUNIT_CASE(string_test_strspn),
-- 
2.25.1