[PATCH v2 7/7] ubsan: Expand tests and reporting

Kees Cook
2020-12-03T00:46:28Z

Expand the UBSAN tests to include some additional UB cases. Notably the
out-of-bounds enum loading appears not to work. Also include per-test
reporting, including the relevant CONFIG_UBSAN... Kconfigs.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
lib/test_ubsan.c | 74 ++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 66 insertions(+), 8 deletions(-)

diff --git a/lib/test_ubsan.c b/lib/test_ubsan.c
index 9ea10adf7a66..5e5d9355ef49 100644
--- a/lib/test_ubsan.c
+++ b/lib/test_ubsan.c
@@ -5,32 +5,54 @@

typedef void(*test_ubsan_fp)(void);

+#define UBSAN_TEST(config, ...) do { \
+ pr_info("%s " __VA_ARGS__ "%s(%s=%s)\n", __func__, \
+ sizeof(" " __VA_ARGS__) > 2 ? " " : "", \
+ #config, IS_ENABLED(config) ? "y" : "n"); \
+ } while (0)
+
static void test_ubsan_add_overflow(void)
{
volatile int val = INT_MAX;
+ volatile unsigned int uval = UINT_MAX;

+ UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW);
val += 2;
+
+ UBSAN_TEST(CONFIG_UBSAN_UNSIGNED_OVERFLOW);
+ uval += 2;
}

static void test_ubsan_sub_overflow(void)
{
volatile int val = INT_MIN;
+ volatile unsigned int uval = 0;
volatile int val2 = 2;

+ UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW);
val -= val2;
+
+ UBSAN_TEST(CONFIG_UBSAN_UNSIGNED_OVERFLOW);
+ uval -= val2;
}

static void test_ubsan_mul_overflow(void)
{
volatile int val = INT_MAX / 2;
+ volatile unsigned int uval = UINT_MAX / 2;

+ UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW);
val *= 3;
+
+ UBSAN_TEST(CONFIG_UBSAN_UNSIGNED_OVERFLOW);
+ uval *= 3;
}

static void test_ubsan_negate_overflow(void)
{
volatile int val = INT_MIN;

+ UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW);
val = -val;
}

@@ -39,37 +61,67 @@ static void test_ubsan_divrem_overflow(void)
volatile int val = 16;
volatile int val2 = 0;

+ UBSAN_TEST(CONFIG_UBSAN_DIV_ZERO);
val /= val2;
}

static void test_ubsan_shift_out_of_bounds(void)
{
- volatile int val = -1;
- int val2 = 10;
+ volatile int neg = -1, wrap = 4;
+ int val1 = 10;
+ int val2 = INT_MAX;
+
+ UBSAN_TEST(CONFIG_UBSAN_SHIFT, "negative exponent");
+ val1 <<= neg;

- val2 <<= val;
+ UBSAN_TEST(CONFIG_UBSAN_SHIFT, "left overflow");
+ val2 <<= wrap;
}

static void test_ubsan_out_of_bounds(void)
{
- volatile int i = 4, j = 5;
+ volatile int i = 4, j = 5, k = -1;
+ volatile char above[4] = { }; /* Protect surrounding memory. */
volatile int arr[4];
+ volatile char below[4] = { }; /* Protect surrounding memory. */

+ above[0] = below[0];
+
+ UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "above");
arr[j] = i;
+
+ UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "below");
+ arr[k] = i;
}

+enum ubsan_test_enum {
+ UBSAN_TEST_ZERO = 0,
+ UBSAN_TEST_ONE,
+ UBSAN_TEST_MAX,
+};
+
static void test_ubsan_load_invalid_value(void)
{
volatile char *dst, *src;
bool val, val2, *ptr;
- char c = 4;
+ enum ubsan_test_enum eval, eval2, *eptr;
+ unsigned char c = 0xff;

+ UBSAN_TEST(CONFIG_UBSAN_BOOL, "bool");
dst = (char *)&val;
src = &c;
*dst = *src;

ptr = &val2;
val2 = val;
+
+ UBSAN_TEST(CONFIG_UBSAN_ENUM, "enum");
+ dst = (char *)&eval;
+ src = &c;
+ *dst = *src;
+
+ eptr = &eval2;
+ eval2 = eval;
}

static void test_ubsan_null_ptr_deref(void)
@@ -77,6 +129,7 @@ static void test_ubsan_null_ptr_deref(void)
volatile int *ptr = NULL;
int val;

+ UBSAN_TEST(CONFIG_UBSAN_OBJECT_SIZE);
val = *ptr;
}

@@ -85,6 +138,7 @@ static void test_ubsan_misaligned_access(void)
volatile char arr[5] __aligned(4) = {1, 2, 3, 4, 5};
volatile int *ptr, val = 6;

+ UBSAN_TEST(CONFIG_UBSAN_ALIGNMENT);
ptr = (int *)(arr + 1);
*ptr = val;
}
@@ -95,6 +149,7 @@ static void test_ubsan_object_size_mismatch(void)
volatile int val __aligned(8) = 4;
volatile long long *ptr, val2;

+ UBSAN_TEST(CONFIG_UBSAN_OBJECT_SIZE);
ptr = (long long *)&val;
val2 = *ptr;
}
@@ -104,15 +159,19 @@ static const test_ubsan_fp test_ubsan_array[] = {
test_ubsan_sub_overflow,
test_ubsan_mul_overflow,
test_ubsan_negate_overflow,
- test_ubsan_divrem_overflow,
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,
};

+/* Excluded because they Oops the module. */
+static const test_ubsan_fp skip_ubsan_array[] = {
+ test_ubsan_divrem_overflow,
+ test_ubsan_null_ptr_deref,
+};
+
static int __init test_ubsan_init(void)
{
unsigned int i;
@@ -120,7 +179,6 @@ static int __init test_ubsan_init(void)
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);
--
2.25.1