fortify: Add KUnit tests for runtime overflows

With fortify overflows able to be redirected, we can use KUnit to
exercise the overflow conditions. Add tests for every API covered by
CONFIG_FORTIFY_SOURCE, except for memset() and memcpy(), which are
special-cased for now.

Disable warnings in the Makefile since we're explicitly testing
known-bad string handling code patterns.

Note that this makes the LKDTM FORTIFY_STR* tests obsolete, but those
can be removed separately.

Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/lib/Makefile b/lib/Makefile
index bc36a5c167dbe177fb384d145056e4499d042302..eae87c41b22b1acdb517d654c67c6093a73d2aee 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -402,6 +402,8 @@ obj-$(CONFIG_OVERFLOW_KUNIT_TEST) += overflow_kunit.o
 CFLAGS_stackinit_kunit.o += $(call cc-disable-warning, switch-unreachable)
 obj-$(CONFIG_STACKINIT_KUNIT_TEST) += stackinit_kunit.o
 CFLAGS_fortify_kunit.o += $(call cc-disable-warning, unsequenced)
+CFLAGS_fortify_kunit.o += $(call cc-disable-warning, stringop-overread)
+CFLAGS_fortify_kunit.o += $(call cc-disable-warning, stringop-truncation)
 CFLAGS_fortify_kunit.o += $(DISABLE_STRUCTLEAK_PLUGIN)
 obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o
 obj-$(CONFIG_STRCAT_KUNIT_TEST) += strcat_kunit.o

diff --git a/lib/fortify_kunit.c b/lib/fortify_kunit.c
index 4ba7d02fdd7812d42d51b342cfbbf0a820ada7fb..f0accebeca02f97ee9646d8e81c1fe74e487d882 100644 (file)
--- a/lib/fortify_kunit.c
+++ b/lib/fortify_kunit.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Runtime test cases for CONFIG_FORTIFY_SOURCE that aren't expected to
- * Oops the kernel on success. (For those, see drivers/misc/lkdtm/fortify.c)
+ * Runtime test cases for CONFIG_FORTIFY_SOURCE. For testing memcpy(),
+ * see FORTIFY_MEM_* tests in LKDTM (drivers/misc/lkdtm/fortify.c).
  *
  * For corner cases with UBSAN, try testing with:
  *
@@ -346,6 +346,594 @@ DEFINE_ALLOC_SIZE_TEST_PAIR(kvmalloc)
 } while (0)
 DEFINE_ALLOC_SIZE_TEST_PAIR(devm_kmalloc)
 
+/*
+ * We can't have an array at the end of a structure or else
+ * builds without -fstrict-flex-arrays=3 will report them as
+ * being an unknown length. Additionally, add bytes before
+ * and after the string to catch over/underflows if tests
+ * fail.
+ */
+struct fortify_padding {
+       unsigned long bytes_before;
+       char buf[32];
+       unsigned long bytes_after;
+};
+/* Force compiler into not being able to resolve size at compile-time. */
+static volatile int unconst;
+
+static void strlen_test(struct kunit *test)
+{
+       struct fortify_padding pad = { };
+       int i, end = sizeof(pad.buf) - 1;
+
+       /* Fill 31 bytes with valid characters. */
+       for (i = 0; i < sizeof(pad.buf) - 1; i++)
+               pad.buf[i] = i + '0';
+       /* Trailing bytes are still %NUL. */
+       KUNIT_EXPECT_EQ(test, pad.buf[end], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* String is terminated, so strlen() is valid. */
+       KUNIT_EXPECT_EQ(test, strlen(pad.buf), end);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+
+       /* Make string unterminated, and recount. */
+       pad.buf[end] = 'A';
+       end = sizeof(pad.buf);
+       KUNIT_EXPECT_EQ(test, strlen(pad.buf), end);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
+}
+
+static void strnlen_test(struct kunit *test)
+{
+       struct fortify_padding pad = { };
+       int i, end = sizeof(pad.buf) - 1;
+
+       /* Fill 31 bytes with valid characters. */
+       for (i = 0; i < sizeof(pad.buf) - 1; i++)
+               pad.buf[i] = i + '0';
+       /* Trailing bytes are still %NUL. */
+       KUNIT_EXPECT_EQ(test, pad.buf[end], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* String is terminated, so strnlen() is valid. */
+       KUNIT_EXPECT_EQ(test, strnlen(pad.buf, sizeof(pad.buf)), end);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       /* A truncated strnlen() will be safe, too. */
+       KUNIT_EXPECT_EQ(test, strnlen(pad.buf, sizeof(pad.buf) / 2),
+                                       sizeof(pad.buf) / 2);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+
+       /* Make string unterminated, and recount. */
+       pad.buf[end] = 'A';
+       end = sizeof(pad.buf);
+       /* Reading beyond with strncpy() will fail. */
+       KUNIT_EXPECT_EQ(test, strnlen(pad.buf, end + 1), end);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
+       KUNIT_EXPECT_EQ(test, strnlen(pad.buf, end + 2), end);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
+
+       /* Early-truncated is safe still, though. */
+       KUNIT_EXPECT_EQ(test, strnlen(pad.buf, end), end);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
+
+       end = sizeof(pad.buf) / 2;
+       KUNIT_EXPECT_EQ(test, strnlen(pad.buf, end), end);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
+}
+
+static void strcpy_test(struct kunit *test)
+{
+       struct fortify_padding pad = { };
+       char src[sizeof(pad.buf) + 1] = { };
+       int i;
+
+       /* Fill 31 bytes with valid characters. */
+       for (i = 0; i < sizeof(src) - 2; i++)
+               src[i] = i + '0';
+
+       /* Destination is %NUL-filled to start with. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Legitimate strcpy() 1 less than of max size. */
+       KUNIT_ASSERT_TRUE(test, strcpy(pad.buf, src)
+                               == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Only last byte should be %NUL */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+
+       src[sizeof(src) - 2] = 'A';
+       /* But now we trip the overflow checking. */
+       KUNIT_ASSERT_TRUE(test, strcpy(pad.buf, src)
+                               == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
+       /* Trailing %NUL -- thanks to FORTIFY. */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       /* And we will not have gone beyond. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       src[sizeof(src) - 1] = 'A';
+       /* And for sure now, two bytes past. */
+       KUNIT_ASSERT_TRUE(test, strcpy(pad.buf, src)
+                               == pad.buf);
+       /*
+        * Which trips both the strlen() on the unterminated src,
+        * and the resulting copy attempt.
+        */
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
+       /* Trailing %NUL -- thanks to FORTIFY. */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       /* And we will not have gone beyond. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+}
+
+static void strncpy_test(struct kunit *test)
+{
+       struct fortify_padding pad = { };
+       char src[] = "Copy me fully into a small buffer and I will overflow!";
+
+       /* Destination is %NUL-filled to start with. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Legitimate strncpy() 1 less than of max size. */
+       KUNIT_ASSERT_TRUE(test, strncpy(pad.buf, src,
+                                       sizeof(pad.buf) + unconst - 1)
+                               == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Only last byte should be %NUL */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+
+       /* Legitimate (though unterminated) max-size strncpy. */
+       KUNIT_ASSERT_TRUE(test, strncpy(pad.buf, src,
+                                       sizeof(pad.buf) + unconst)
+                               == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* No trailing %NUL -- thanks strncpy API. */
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       /* But we will not have gone beyond. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Now verify that FORTIFY is working... */
+       KUNIT_ASSERT_TRUE(test, strncpy(pad.buf, src,
+                                       sizeof(pad.buf) + unconst + 1)
+                               == pad.buf);
+       /* Should catch the overflow. */
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       /* And we will not have gone beyond. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* And further... */
+       KUNIT_ASSERT_TRUE(test, strncpy(pad.buf, src,
+                                       sizeof(pad.buf) + unconst + 2)
+                               == pad.buf);
+       /* Should catch the overflow. */
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       /* And we will not have gone beyond. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+}
+
+static void strscpy_test(struct kunit *test)
+{
+       struct fortify_padding pad = { };
+       char src[] = "Copy me fully into a small buffer and I will overflow!";
+
+       /* Destination is %NUL-filled to start with. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Legitimate strscpy() 1 less than of max size. */
+       KUNIT_ASSERT_EQ(test, strscpy(pad.buf, src,
+                                     sizeof(pad.buf) + unconst - 1),
+                       -E2BIG);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Keeping space for %NUL, last two bytes should be %NUL */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+
+       /* Legitimate max-size strscpy. */
+       KUNIT_ASSERT_EQ(test, strscpy(pad.buf, src,
+                                     sizeof(pad.buf) + unconst),
+                       -E2BIG);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* A trailing %NUL will exist. */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+
+       /* Now verify that FORTIFY is working... */
+       KUNIT_ASSERT_EQ(test, strscpy(pad.buf, src,
+                                     sizeof(pad.buf) + unconst + 1),
+                       -E2BIG);
+       /* Should catch the overflow. */
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       /* And we will not have gone beyond. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* And much further... */
+       KUNIT_ASSERT_EQ(test, strscpy(pad.buf, src,
+                                     sizeof(src) * 2 + unconst),
+                       -E2BIG);
+       /* Should catch the overflow. */
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       /* And we will not have gone beyond. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+}
+
+static void strcat_test(struct kunit *test)
+{
+       struct fortify_padding pad = { };
+       char src[sizeof(pad.buf) / 2] = { };
+       char one[] = "A";
+       char two[] = "BC";
+       int i;
+
+       /* Fill 15 bytes with valid characters. */
+       for (i = 0; i < sizeof(src) - 1; i++)
+               src[i] = i + 'A';
+
+       /* Destination is %NUL-filled to start with. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Legitimate strcat() using less than half max size. */
+       KUNIT_ASSERT_TRUE(test, strcat(pad.buf, src) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Legitimate strcat() now 2 bytes shy of end. */
+       KUNIT_ASSERT_TRUE(test, strcat(pad.buf, src) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Last two bytes should be %NUL */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+
+       /* Add one more character to the end. */
+       KUNIT_ASSERT_TRUE(test, strcat(pad.buf, one) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Last byte should be %NUL */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+
+       /* And this one char will overflow. */
+       KUNIT_ASSERT_TRUE(test, strcat(pad.buf, one) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
+       /* Last byte should be %NUL thanks to FORTIFY. */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* And adding two will overflow more. */
+       KUNIT_ASSERT_TRUE(test, strcat(pad.buf, two) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
+       /* Last byte should be %NUL thanks to FORTIFY. */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+}
+
+static void strncat_test(struct kunit *test)
+{
+       struct fortify_padding pad = { };
+       char src[sizeof(pad.buf)] = { };
+       int i, partial;
+
+       /* Fill 31 bytes with valid characters. */
+       partial = sizeof(src) / 2 - 1;
+       for (i = 0; i < partial; i++)
+               src[i] = i + 'A';
+
+       /* Destination is %NUL-filled to start with. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Legitimate strncat() using less than half max size. */
+       KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, partial) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Legitimate strncat() now 2 bytes shy of end. */
+       KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, partial) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Last two bytes should be %NUL */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+
+       /* Add one more character to the end. */
+       KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, 1) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Last byte should be %NUL */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+
+       /* And this one char will overflow. */
+       KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, 1) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
+       /* Last byte should be %NUL thanks to FORTIFY. */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* And adding two will overflow more. */
+       KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, 2) == pad.buf);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
+       /* Last byte should be %NUL thanks to FORTIFY. */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Force an unterminated destination, and overflow. */
+       pad.buf[sizeof(pad.buf) - 1] = 'A';
+       KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, 1) == pad.buf);
+       /* This will have tripped both strlen() and strcat(). */
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 3);
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       /* But we should not go beyond the end. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+}
+
+static void strlcat_test(struct kunit *test)
+{
+       struct fortify_padding pad = { };
+       char src[sizeof(pad.buf)] = { };
+       int i, partial;
+       int len = sizeof(pad.buf) + unconst;
+
+       /* Fill 15 bytes with valid characters. */
+       partial = sizeof(src) / 2 - 1;
+       for (i = 0; i < partial; i++)
+               src[i] = i + 'A';
+
+       /* Destination is %NUL-filled to start with. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Legitimate strlcat() using less than half max size. */
+       KUNIT_ASSERT_EQ(test, strlcat(pad.buf, src, len), partial);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Legitimate strlcat() now 2 bytes shy of end. */
+       KUNIT_ASSERT_EQ(test, strlcat(pad.buf, src, len), partial * 2);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Last two bytes should be %NUL */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+
+       /* Add one more character to the end. */
+       KUNIT_ASSERT_EQ(test, strlcat(pad.buf, "Q", len), partial * 2 + 1);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
+       /* Last byte should be %NUL */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+
+       /* And this one char will overflow. */
+       KUNIT_ASSERT_EQ(test, strlcat(pad.buf, "V", len * 2), len);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
+       /* Last byte should be %NUL thanks to FORTIFY. */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* And adding two will overflow more. */
+       KUNIT_ASSERT_EQ(test, strlcat(pad.buf, "QQ", len * 2), len + 1);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
+       /* Last byte should be %NUL thanks to FORTIFY. */
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Force an unterminated destination, and overflow. */
+       pad.buf[sizeof(pad.buf) - 1] = 'A';
+       KUNIT_ASSERT_EQ(test, strlcat(pad.buf, "TT", len * 2), len + 2);
+       /* This will have tripped both strlen() and strlcat(). */
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
+       KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
+       /* But we should not go beyond the end. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+
+       /* Force an unterminated source, and overflow. */
+       memset(src, 'B', sizeof(src));
+       pad.buf[sizeof(pad.buf) - 1] = '\0';
+       KUNIT_ASSERT_EQ(test, strlcat(pad.buf, src, len * 3), len - 1 + sizeof(src));
+       /* This will have tripped both strlen() and strlcat(). */
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 3);
+       KUNIT_EXPECT_EQ(test, fortify_write_overflows, 3);
+       KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
+       /* But we should not go beyond the end. */
+       KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
+}
+
+static void memscan_test(struct kunit *test)
+{
+       char haystack[] = "Where oh where is my memory range?";
+       char *mem = haystack + strlen("Where oh where is ");
+       char needle = 'm';
+       size_t len = sizeof(haystack) + unconst;
+
+       KUNIT_ASSERT_PTR_EQ(test, memscan(haystack, needle, len),
+                                 mem);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       /* Catch too-large range. */
+       KUNIT_ASSERT_PTR_EQ(test, memscan(haystack, needle, len + 1),
+                                 NULL);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
+       KUNIT_ASSERT_PTR_EQ(test, memscan(haystack, needle, len * 2),
+                                 NULL);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
+}
+
+static void memchr_test(struct kunit *test)
+{
+       char haystack[] = "Where oh where is my memory range?";
+       char *mem = haystack + strlen("Where oh where is ");
+       char needle = 'm';
+       size_t len = sizeof(haystack) + unconst;
+
+       KUNIT_ASSERT_PTR_EQ(test, memchr(haystack, needle, len),
+                                 mem);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       /* Catch too-large range. */
+       KUNIT_ASSERT_PTR_EQ(test, memchr(haystack, needle, len + 1),
+                                 NULL);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
+       KUNIT_ASSERT_PTR_EQ(test, memchr(haystack, needle, len * 2),
+                                 NULL);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
+}
+
+static void memchr_inv_test(struct kunit *test)
+{
+       char haystack[] = "Where oh where is my memory range?";
+       char *mem = haystack + 1;
+       char needle = 'W';
+       size_t len = sizeof(haystack) + unconst;
+
+       /* Normal search is okay. */
+       KUNIT_ASSERT_PTR_EQ(test, memchr_inv(haystack, needle, len),
+                                 mem);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       /* Catch too-large range. */
+       KUNIT_ASSERT_PTR_EQ(test, memchr_inv(haystack, needle, len + 1),
+                                 NULL);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
+       KUNIT_ASSERT_PTR_EQ(test, memchr_inv(haystack, needle, len * 2),
+                                 NULL);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
+}
+
+static void memcmp_test(struct kunit *test)
+{
+       char one[] = "My mind is going ...";
+       char two[] = "My mind is going ... I can feel it.";
+       size_t one_len = sizeof(one) + unconst - 1;
+       size_t two_len = sizeof(two) + unconst - 1;
+
+       /* We match the first string (ignoring the %NUL). */
+       KUNIT_ASSERT_EQ(test, memcmp(one, two, one_len), 0);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       /* Still in bounds, but no longer matching. */
+       KUNIT_ASSERT_EQ(test, memcmp(one, two, one_len + 1), -32);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+
+       /* Catch too-large ranges. */
+       KUNIT_ASSERT_EQ(test, memcmp(one, two, one_len + 2), INT_MIN);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
+
+       KUNIT_ASSERT_EQ(test, memcmp(two, one, two_len + 2), INT_MIN);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
+}
+
+static void kmemdup_test(struct kunit *test)
+{
+       char src[] = "I got Doom running on it!";
+       char *copy;
+       size_t len = sizeof(src) + unconst;
+
+       /* Copy is within bounds. */
+       copy = kmemdup(src, len, GFP_KERNEL);
+       KUNIT_EXPECT_NOT_NULL(test, copy);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       kfree(copy);
+
+       /* Without %NUL. */
+       copy = kmemdup(src, len - 1, GFP_KERNEL);
+       KUNIT_EXPECT_NOT_NULL(test, copy);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       kfree(copy);
+
+       /* Tiny bounds. */
+       copy = kmemdup(src, 1, GFP_KERNEL);
+       KUNIT_EXPECT_NOT_NULL(test, copy);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
+       kfree(copy);
+
+       /* Out of bounds by 1 byte. */
+       copy = kmemdup(src, len + 1, GFP_KERNEL);
+       KUNIT_EXPECT_NULL(test, copy);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
+       kfree(copy);
+
+       /* Way out of bounds. */
+       copy = kmemdup(src, len * 2, GFP_KERNEL);
+       KUNIT_EXPECT_NULL(test, copy);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
+       kfree(copy);
+
+       /* Starting offset causing out of bounds. */
+       copy = kmemdup(src + 1, len, GFP_KERNEL);
+       KUNIT_EXPECT_NULL(test, copy);
+       KUNIT_EXPECT_EQ(test, fortify_read_overflows, 3);
+       kfree(copy);
+}
+
 static int fortify_test_init(struct kunit *test)
 {
        if (!IS_ENABLED(CONFIG_FORTIFY_SOURCE))
@@ -373,6 +961,21 @@ static struct kunit_case fortify_test_cases[] = {
        KUNIT_CASE(alloc_size_kvmalloc_dynamic_test),
        KUNIT_CASE(alloc_size_devm_kmalloc_const_test),
        KUNIT_CASE(alloc_size_devm_kmalloc_dynamic_test),
+       KUNIT_CASE(strlen_test),
+       KUNIT_CASE(strnlen_test),
+       KUNIT_CASE(strcpy_test),
+       KUNIT_CASE(strncpy_test),
+       KUNIT_CASE(strscpy_test),
+       KUNIT_CASE(strcat_test),
+       KUNIT_CASE(strncat_test),
+       KUNIT_CASE(strlcat_test),
+       /* skip memset: performs bounds checking on whole structs */
+       /* skip memcpy: still using warn-and-overwrite instead of hard-fail */
+       KUNIT_CASE(memscan_test),
+       KUNIT_CASE(memchr_test),
+       KUNIT_CASE(memchr_inv_test),
+       KUNIT_CASE(memcmp_test),
+       KUNIT_CASE(kmemdup_test),
        {}
 };