From: Feng Jiang <jiangfeng@kylinos.cn>
Date: Sat, 4 Apr 2026 01:28:47 +0000 (-0600)
Subject: lib/string_kunit: add correctness test for strrchr()
X-Git-Tag: v7.1-rc1~27^2~11
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=27b2810a4a3dcd1545ec8bafc82f967eda591c47;p=thirdparty%2Fkernel%2Flinux.git

lib/string_kunit: add correctness test for strrchr()

Add a KUnit test for strrchr() to verify correctness across
different string lengths and memory alignments. Use vmalloc()
to place the NUL character at the page boundary to ensure
over-reads are detected.

Suggested-by: Kees Cook <kees@kernel.org>
Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn>
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20260130025018.172925-4-jiangfeng@kylinos.cn
Signed-off-by: Paul Walmsley <pjw@kernel.org>
---

diff --git a/lib/tests/string_kunit.c b/lib/tests/string_kunit.c
index 1c2d57e05624..2bed641e1eae 100644
--- a/lib/tests/string_kunit.c
+++ b/lib/tests/string_kunit.c
@@ -190,6 +190,36 @@ static void string_test_strchr(struct kunit *test)
 	KUNIT_ASSERT_NULL(test, result);
 }
 
+static void string_test_strrchr(struct kunit *test)
+{
+	size_t buf_size;
+	char *buf, *s;
+
+	buf_size = PAGE_ALIGN(STRING_TEST_MAX_LEN + STRING_TEST_MAX_OFFSET + 1);
+	buf = vmalloc(buf_size);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf);
+
+	memset(buf, 'A', buf_size);
+
+	for (size_t offset = 0; offset < STRING_TEST_MAX_OFFSET; offset++) {
+		for (size_t len = 0; len <= STRING_TEST_MAX_LEN; len++) {
+			s = buf + buf_size - 1 - offset - len;
+			s[len] = '\0';
+
+			KUNIT_EXPECT_PTR_EQ(test, strrchr(s, 'Z'), NULL);
+
+			if (len > 0)
+				KUNIT_EXPECT_PTR_EQ(test, strrchr(s, 'A'), s + len - 1);
+			else
+				KUNIT_EXPECT_PTR_EQ(test, strrchr(s, 'A'), NULL);
+
+			s[len] = 'A';
+		}
+	}
+
+	vfree(buf);
+}
+
 static void string_test_strnchr(struct kunit *test)
 {
 	const char *test_string = "abcdefghijkl";
@@ -685,6 +715,7 @@ static struct kunit_case string_test_cases[] = {
 	KUNIT_CASE(string_test_strnlen),
 	KUNIT_CASE(string_test_strchr),
 	KUNIT_CASE(string_test_strnchr),
+	KUNIT_CASE(string_test_strrchr),
 	KUNIT_CASE(string_test_strspn),
 	KUNIT_CASE(string_test_strcmp),
 	KUNIT_CASE(string_test_strcmp_long_strings),