lib: add testing module for UBSAN

This is a test module for UBSAN.  It triggers all undefined behaviors
that linux supports now, and detect them.

All test-cases have passed by compiling with gcc-5.5.0.

If use gcc-4.9.x, misaligned, out-of-bounds, object-size-mismatch will not
be detected.  Because gcc-4.9.x doesn't support them.

Link: http://lkml.kernel.org/r/20180309102247.GA2944@pjb1027-Latitude-E5410
Signed-off-by: Jinbum Park <jinb.park7@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/Kconfig.ubsan

@@ -46,3 +46,10 @@ config UBSAN_NULL
 	help
 	  This option enables detection of memory accesses via a
 	  null pointer.
+
+config TEST_UBSAN
+	tristate "Module for testing for undefined behavior detection"
+	depends on m && UBSAN
+	help
+	  This is a test module for UBSAN.
+	  It triggers various undefined behavior, and detect it.

lib/Makefile

@@ -54,6 +54,8 @@ obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o
 obj-$(CONFIG_TEST_HASH) += test_hash.o test_siphash.o
 obj-$(CONFIG_TEST_KASAN) += test_kasan.o
 CFLAGS_test_kasan.o += -fno-builtin
+obj-$(CONFIG_TEST_UBSAN) += test_ubsan.o
+UBSAN_SANITIZE_test_ubsan.o := y
 obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o
 obj-$(CONFIG_TEST_LIST_SORT) += test_list_sort.o
 obj-$(CONFIG_TEST_LKM) += test_module.o

lib/test_ubsan.c

@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+typedef void(*test_ubsan_fp)(void);
+
+static void test_ubsan_add_overflow(void)
+{
+	volatile int val = INT_MAX;
+
+	val += 2;
+}
+
+static void test_ubsan_sub_overflow(void)
+{
+	volatile int val = INT_MIN;
+	volatile int val2 = 2;
+
+	val -= val2;
+}
+
+static void test_ubsan_mul_overflow(void)
+{
+	volatile int val = INT_MAX / 2;
+
+	val *= 3;
+}
+
+static void test_ubsan_negate_overflow(void)
+{
+	volatile int val = INT_MIN;
+
+	val = -val;
+}
+
+static void test_ubsan_divrem_overflow(void)
+{
+	volatile int val = 16;
+	volatile int val2 = 0;
+
+	val /= val2;
+}
+
+static void test_ubsan_vla_bound_not_positive(void)
+{
+	volatile int size = -1;
+	char buf[size];
+
+	(void)buf;
+}
+
+static void test_ubsan_shift_out_of_bounds(void)
+{
+	volatile int val = -1;
+	int val2 = 10;
+
+	val2 <<= val;
+}
+
+static void test_ubsan_out_of_bounds(void)
+{
+	volatile int i = 4, j = 5;
+	volatile int arr[i];
+
+	arr[j] = i;
+}
+
+static void test_ubsan_load_invalid_value(void)
+{
+	volatile char *dst, *src;
+	bool val, val2, *ptr;
+	char c = 4;
+
+	dst = (char *)&val;
+	src = &c;
+	*dst = *src;
+
+	ptr = &val2;
+	val2 = val;
+}
+
+static void test_ubsan_null_ptr_deref(void)
+{
+	volatile int *ptr = NULL;
+	int val;
+
+	val = *ptr;
+}
+
+void test_ubsan_misaligned_access(void)
+{
+	volatile char arr[5] __aligned(4) = {1, 2, 3, 4, 5};
+	volatile int *ptr, val = 6;
+
+	ptr = (int *)(arr + 1);
+	*ptr = val;
+}
+
+static void test_ubsan_object_size_mismatch(void)
+{
+	/* "((aligned(8)))" helps this not into be misaligned for ptr-access. */
+	volatile int val __aligned(8) = 4;
+	volatile long long *ptr, val2;
+
+	ptr = (long long *)&val;
+	val2 = *ptr;
+}
+
+static const test_ubsan_fp test_ubsan_array[] = {
+	test_ubsan_add_overflow,
+	test_ubsan_sub_overflow,
+	test_ubsan_mul_overflow,
+	test_ubsan_negate_overflow,
+	test_ubsan_divrem_overflow,
+	test_ubsan_vla_bound_not_positive,
+	test_ubsan_shift_out_of_bounds,
+	test_ubsan_out_of_bounds,
+	test_ubsan_load_invalid_value,
+	//test_ubsan_null_ptr_deref, /* exclude it because there is a crash */
+	test_ubsan_misaligned_access,
+	test_ubsan_object_size_mismatch,
+};
+
+static int __init test_ubsan_init(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(test_ubsan_array); i++)
+		test_ubsan_array[i]();
+
+	(void)test_ubsan_null_ptr_deref; /* to avoid unsed-function warning */
+	return 0;
+}
+module_init(test_ubsan_init);
+
+static void __exit test_ubsan_exit(void)
+{
+	/* do nothing */
+}
+module_exit(test_ubsan_exit);
+
+MODULE_AUTHOR("Jinbum Park <jinb.park7@gmail.com>");
+MODULE_LICENSE("GPL v2");