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Message-Id: <20230406000212.3442647-3-keescook@chromium.org>
Date:   Wed,  5 Apr 2023 17:02:02 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-hardening@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>, Kees Cook <kees@...flux.net>,
        Andy Shevchenko <andy@...nel.org>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Puyou Lu <puyou.lu@...il.com>, Mark Brown <broonie@...nel.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Brendan Higgins <brendan.higgins@...ux.dev>,
        David Gow <davidgow@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Miguel Ojeda <ojeda@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Liam Howlett <liam.howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Yury Norov <yury.norov@...il.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Sander Vanheule <sander@...nheule.net>,
        Eric Biggers <ebiggers@...gle.com>,
        "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Daniel Latypov <dlatypov@...gle.com>,
        José Expósito <jose.exposito89@...il.com>,
        linux-kernel@...r.kernel.org, kunit-dev@...glegroups.com
Subject: [PATCH 3/9] string: Add Kunit tests for strcat() family

From: Kees Cook <kees@...flux.net>

Add tests to make sure the strcat() family of functions behave
correctly.

Signed-off-by: Kees Cook <kees@...flux.net>
---
 MAINTAINERS        |   1 +
 lib/Kconfig.debug  |   5 +++
 lib/Makefile       |   1 +
 lib/strcat_kunit.c | 100 +++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 107 insertions(+)
 create mode 100644 lib/strcat_kunit.c

diff --git a/MAINTAINERS b/MAINTAINERS
index ec57c42ed544..86c0012b5130 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8021,6 +8021,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/har
 F:	include/linux/fortify-string.h
 F:	lib/fortify_kunit.c
 F:	lib/memcpy_kunit.c
+F:	lib/strcat_kunit.c
 F:	lib/strscpy_kunit.c
 F:	lib/test_fortify/*
 F:	scripts/test_fortify.sh
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index d48a5f4b471e..86157aa5e979 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2631,6 +2631,11 @@ config HW_BREAKPOINT_KUNIT_TEST
 
 	  If unsure, say N.
 
+config STRCAT_KUNIT_TEST
+	tristate "Test strcat() family of functions at runtime" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+
 config STRSCPY_KUNIT_TEST
 	tristate "Test strscpy*() family of functions at runtime" if !KUNIT_ALL_TESTS
 	depends on KUNIT
diff --git a/lib/Makefile b/lib/Makefile
index baf2821f7a00..6582d8fe1a77 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -389,6 +389,7 @@ obj-$(CONFIG_STACKINIT_KUNIT_TEST) += stackinit_kunit.o
 CFLAGS_fortify_kunit.o += $(call cc-disable-warning, unsequenced)
 CFLAGS_fortify_kunit.o += $(DISABLE_STRUCTLEAK_PLUGIN)
 obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o
+obj-$(CONFIG_STRCAT_KUNIT_TEST) += strcat_kunit.o
 obj-$(CONFIG_STRSCPY_KUNIT_TEST) += strscpy_kunit.o
 obj-$(CONFIG_SIPHASH_KUNIT_TEST) += siphash_kunit.o
 
diff --git a/lib/strcat_kunit.c b/lib/strcat_kunit.c
new file mode 100644
index 000000000000..b6428c3a557f
--- /dev/null
+++ b/lib/strcat_kunit.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Kernel module for testing 'strcat' family of functions.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <kunit/test.h>
+#include <linux/string.h>
+
+static void strcat_test(struct kunit *test)
+{
+	char dest[8];
+
+	/* Destination is terminated. */
+	memset(dest, 0, sizeof(dest));
+	KUNIT_EXPECT_EQ(test, strlen(dest), 0);
+	/* Empty copy does nothing. */
+	KUNIT_EXPECT_TRUE(test, strcat(dest, "") == dest);
+	KUNIT_EXPECT_STREQ(test, dest, "");
+	/* 4 characters copied in, stops at %NUL. */
+	KUNIT_EXPECT_TRUE(test, strcat(dest, "four\000123") == dest);
+	KUNIT_EXPECT_STREQ(test, dest, "four");
+	KUNIT_EXPECT_EQ(test, dest[5], '\0');
+	/* 2 more characters copied in okay. */
+	KUNIT_EXPECT_TRUE(test, strcat(dest, "AB") == dest);
+	KUNIT_EXPECT_STREQ(test, dest, "fourAB");
+}
+
+static void strncat_test(struct kunit *test)
+{
+	char dest[8];
+
+	/* Destination is terminated. */
+	memset(dest, 0, sizeof(dest));
+	KUNIT_EXPECT_EQ(test, strlen(dest), 0);
+	/* Empty copy of size 0 does nothing. */
+	KUNIT_EXPECT_TRUE(test, strncat(dest, "", 0) == dest);
+	KUNIT_EXPECT_STREQ(test, dest, "");
+	/* Empty copy of size 1 does nothing too. */
+	KUNIT_EXPECT_TRUE(test, strncat(dest, "", 1) == dest);
+	KUNIT_EXPECT_STREQ(test, dest, "");
+	/* Copy of max 0 characters should do nothing. */
+	KUNIT_EXPECT_TRUE(test, strncat(dest, "asdf", 0) == dest);
+	KUNIT_EXPECT_STREQ(test, dest, "");
+
+	/* 4 characters copied in, even if max is 8. */
+	KUNIT_EXPECT_TRUE(test, strncat(dest, "four\000123", 8) == dest);
+	KUNIT_EXPECT_STREQ(test, dest, "four");
+	KUNIT_EXPECT_EQ(test, dest[5], '\0');
+	/* 2 characters copied in okay, 2 ignored. */
+	KUNIT_EXPECT_TRUE(test, strncat(dest, "ABCD", 2) == dest);
+	KUNIT_EXPECT_STREQ(test, dest, "fourAB");
+}
+
+static void strlcat_test(struct kunit *test)
+{
+	char dest[8] = "";
+
+	/* Destination is terminated. */
+	KUNIT_EXPECT_EQ(test, strlen(dest), 0);
+	/* Empty copy is size 0. */
+	KUNIT_EXPECT_EQ(test, strlcat(dest, "", sizeof(dest)), 0);
+	KUNIT_EXPECT_STREQ(test, dest, "");
+	/* Size 1 should keep buffer terminated, report size of source only. */
+	KUNIT_EXPECT_EQ(test, strlcat(dest, "four", 1), 4);
+	KUNIT_EXPECT_STREQ(test, dest, "");
+
+	/* 4 characters copied in. */
+	KUNIT_EXPECT_EQ(test, strlcat(dest, "four", sizeof(dest)), 4);
+	KUNIT_EXPECT_STREQ(test, dest, "four");
+	/* 2 characters copied in okay, gets to 6 total. */
+	KUNIT_EXPECT_EQ(test, strlcat(dest, "AB", sizeof(dest)), 6);
+	KUNIT_EXPECT_STREQ(test, dest, "fourAB");
+	/* 2 characters ignored if max size (7) reached. */
+	KUNIT_EXPECT_EQ(test, strlcat(dest, "CD", 7), 8);
+	KUNIT_EXPECT_STREQ(test, dest, "fourAB");
+	/* 1 of 2 characters skipped, now at true max size. */
+	KUNIT_EXPECT_EQ(test, strlcat(dest, "EFG", sizeof(dest)), 9);
+	KUNIT_EXPECT_STREQ(test, dest, "fourABE");
+	/* Everything else ignored, now at full size. */
+	KUNIT_EXPECT_EQ(test, strlcat(dest, "1234", sizeof(dest)), 11);
+	KUNIT_EXPECT_STREQ(test, dest, "fourABE");
+}
+
+static struct kunit_case strcat_test_cases[] = {
+	KUNIT_CASE(strcat_test),
+	KUNIT_CASE(strncat_test),
+	KUNIT_CASE(strlcat_test),
+	{}
+};
+
+static struct kunit_suite strcat_test_suite = {
+	.name = "strcat",
+	.test_cases = strcat_test_cases,
+};
+
+kunit_test_suite(strcat_test_suite);
+
+MODULE_LICENSE("GPL");
-- 
2.34.1

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