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Subject[PATCH v4 6/6] lib: Add test module for strscpy_pad
Date
Add a test module for the new strscpy_pad() function.  Tie it into the
kselftest infrastructure for lib/ tests.

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
lib/Kconfig.debug | 3 +
lib/Makefile | 1 +
lib/test_strscpy.c | 150 +++++++++++++++++++++++++
tools/testing/selftests/lib/Makefile | 2 +-
tools/testing/selftests/lib/config | 1 +
tools/testing/selftests/lib/strscpy.sh | 3 +
6 files changed, 159 insertions(+), 1 deletion(-)
create mode 100644 lib/test_strscpy.c
create mode 100755 tools/testing/selftests/lib/strscpy.sh

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 0d9e81779e37..4b644ad399dd 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1769,6 +1769,9 @@ config TEST_HEXDUMP
config TEST_STRING_HELPERS
tristate "Test functions located in the string_helpers module at runtime"

+config TEST_STRSCPY
+ tristate "Test strscpy*() family of functions at runtime"
+
config TEST_KSTRTOX
tristate "Test kstrto*() family of functions at runtime"

diff --git a/lib/Makefile b/lib/Makefile
index 3b08673e8881..b4e08d6234ba 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -70,6 +70,7 @@ obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
obj-$(CONFIG_TEST_PRINTF) += test_printf.o
obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
+obj-$(CONFIG_TEST_STRSCPY) += test_strscpy.o
obj-$(CONFIG_TEST_BITFIELD) += test_bitfield.o
obj-$(CONFIG_TEST_UUID) += test_uuid.o
obj-$(CONFIG_TEST_XARRAY) += test_xarray.o
diff --git a/lib/test_strscpy.c b/lib/test_strscpy.c
new file mode 100644
index 000000000000..a827f94601f5
--- /dev/null
+++ b/lib/test_strscpy.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/string.h>
+
+#include "../tools/testing/selftests/kselftest_module.h"
+
+/*
+ * Kernel module for testing 'strscpy' family of functions.
+ */
+
+KSTM_MODULE_GLOBALS();
+
+/*
+ * tc() - Run a specific test case.
+ * @src: Source string, argument to strscpy_pad()
+ * @count: Size of destination buffer, argument to strscpy_pad()
+ * @expected: Expected return value from call to strscpy_pad()
+ * @terminator: 1 if there should be a terminating null byte 0 otherwise.
+ * @chars: Number of characters from the src string expected to be
+ * written to the dst buffer.
+ * @pad: Number of pad characters expected (in the tail of dst buffer).
+ * (@pad does not include the null terminator byte.)
+ *
+ * Calls strscpy_pad() and verifies the return value and state of the
+ * destination buffer after the call returns.
+ */
+static int __init tc(char *src, int count, int expected,
+ int chars, int terminator, int pad)
+{
+ int nr_bytes_poison;
+ int max_expected;
+ int max_count;
+ int written;
+ char buf[6];
+ int index, i;
+ const char POISON = 'z';
+
+ total_tests++;
+
+ if (!src) {
+ pr_err("null source string not supported\n");
+ return -1;
+ }
+
+ memset(buf, POISON, sizeof(buf));
+ /* Future proofing test suite, validate args */
+ max_count = sizeof(buf) - 2; /* Space for null and to verify overflow */
+ max_expected = count - 1; /* Space for the null */
+ if (count > max_count) {
+ pr_err("count (%d) is too big (%d) ... aborting", count, max_count);
+ return -1;
+ }
+ if (expected > max_expected) {
+ pr_warn("expected (%d) is bigger than can possibly be returned (%d)",
+ expected, max_expected);
+ }
+
+ written = strscpy_pad(buf, src, count);
+ if ((written) != (expected)) {
+ pr_err("%d != %d (written, expected)\n", written, expected);
+ goto fail;
+ }
+
+ if (count && written == -E2BIG) {
+ if (strncmp(buf, src, count - 1) != 0) {
+ pr_err("buffer state invalid for -E2BIG\n");
+ goto fail;
+ }
+ if (buf[count - 1] != '\0') {
+ pr_err("too big string is not null terminated correctly\n");
+ goto fail;
+ }
+ }
+
+ for (i = 0; i < chars; i++) {
+ if (buf[i] != src[i]) {
+ pr_err("buf[i]==%c != src[i]==%c\n", buf[i], src[i]);
+ goto fail;
+ }
+ }
+
+ if (terminator) {
+ if (buf[count - 1] != '\0') {
+ pr_err("string is not null terminated correctly\n");
+ goto fail;
+ }
+ }
+
+ for (i = 0; i < pad; i++) {
+ index = chars + terminator + i;
+ if (buf[index] != '\0') {
+ pr_err("padding missing at index: %d\n", i);
+ goto fail;
+ }
+ }
+
+ nr_bytes_poison = sizeof(buf) - chars - terminator - pad;
+ for (i = 0; i < nr_bytes_poison; i++) {
+ index = sizeof(buf) - 1 - i; /* Check from the end back */
+ if (buf[index] != POISON) {
+ pr_err("poison value missing at index: %d\n", i);
+ goto fail;
+ }
+ }
+
+ return 0;
+fail:
+ failed_tests++;
+ return -1;
+}
+
+static void __init selftest(void)
+{
+ /*
+ * tc() uses a destination buffer of size 6 and needs at
+ * least 2 characters spare (one for null and one to check for
+ * overflow). This means we should only call tc() with
+ * strings up to a maximum of 4 characters long and 'count'
+ * should not exceed 4. To test with longer strings increase
+ * the buffer size in tc().
+ */
+
+ /* tc(src, count, expected, chars, terminator, pad) */
+ KSTM_CHECK_ZERO(tc("a", 0, -E2BIG, 0, 0, 0));
+ KSTM_CHECK_ZERO(tc("", 0, -E2BIG, 0, 0, 0));
+
+ KSTM_CHECK_ZERO(tc("a", 1, -E2BIG, 0, 1, 0));
+ KSTM_CHECK_ZERO(tc("", 1, 0, 0, 1, 0));
+
+ KSTM_CHECK_ZERO(tc("ab", 2, -E2BIG, 1, 1, 0));
+ KSTM_CHECK_ZERO(tc("a", 2, 1, 1, 1, 0));
+ KSTM_CHECK_ZERO(tc("", 2, 0, 0, 1, 1));
+
+ KSTM_CHECK_ZERO(tc("abc", 3, -E2BIG, 2, 1, 0));
+ KSTM_CHECK_ZERO(tc("ab", 3, 2, 2, 1, 0));
+ KSTM_CHECK_ZERO(tc("a", 3, 1, 1, 1, 1));
+ KSTM_CHECK_ZERO(tc("", 3, 0, 0, 1, 2));
+
+ KSTM_CHECK_ZERO(tc("abcd", 4, -E2BIG, 3, 1, 0));
+ KSTM_CHECK_ZERO(tc("abc", 4, 3, 3, 1, 0));
+ KSTM_CHECK_ZERO(tc("ab", 4, 2, 2, 1, 1));
+ KSTM_CHECK_ZERO(tc("a", 4, 1, 1, 1, 2));
+ KSTM_CHECK_ZERO(tc("", 4, 0, 0, 1, 3));
+}
+
+KSTM_MODULE_LOADERS(test_strscpy);
+MODULE_AUTHOR("Tobin C. Harding <tobin@kernel.org>");
+MODULE_LICENSE("GPL");
diff --git a/tools/testing/selftests/lib/Makefile b/tools/testing/selftests/lib/Makefile
index 70d5711e3ac8..9f26635f3e57 100644
--- a/tools/testing/selftests/lib/Makefile
+++ b/tools/testing/selftests/lib/Makefile
@@ -3,6 +3,6 @@
# No binaries, but make sure arg-less "make" doesn't trigger "run_tests"
all:

-TEST_PROGS := printf.sh bitmap.sh prime_numbers.sh
+TEST_PROGS := printf.sh bitmap.sh prime_numbers.sh strscpy.sh

include ../lib.mk
diff --git a/tools/testing/selftests/lib/config b/tools/testing/selftests/lib/config
index 126933bcc950..14a77ea4a8da 100644
--- a/tools/testing/selftests/lib/config
+++ b/tools/testing/selftests/lib/config
@@ -1,3 +1,4 @@
CONFIG_TEST_PRINTF=m
CONFIG_TEST_BITMAP=m
CONFIG_PRIME_NUMBERS=m
+CONFIG_TEST_STRSCPY=m
diff --git a/tools/testing/selftests/lib/strscpy.sh b/tools/testing/selftests/lib/strscpy.sh
new file mode 100755
index 000000000000..71f2be6afba6
--- /dev/null
+++ b/tools/testing/selftests/lib/strscpy.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
+$(dirname $0)/../kselftest_module.sh "strscpy*" test_strscpy
--
2.21.0
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