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557f8c582a
In order to mitigate unexpected signed wrap-around[1], bring back the
signed integer overflow sanitizer. It was removed in commit 6aaa31aeb9
("ubsan: remove overflow checks") because it was effectively a no-op
when combined with -fno-strict-overflow (which correctly changes signed
overflow from being "undefined" to being explicitly "wrap around").
Compilers are adjusting their sanitizers to trap wrap-around and to
detecting common code patterns that should not be instrumented
(e.g. "var + offset < var"). Prepare for this and explicitly rename
the option from "OVERFLOW" to "WRAP" to more accurately describe the
behavior.
To annotate intentional wrap-around arithmetic, the helpers
wrapping_add/sub/mul_wrap() can be used for individual statements. At
the function level, the __signed_wrap attribute can be used to mark an
entire function as expecting its signed arithmetic to wrap around. For a
single object file the Makefile can use "UBSAN_SIGNED_WRAP_target.o := n"
to mark it as wrapping, and for an entire directory, "UBSAN_SIGNED_WRAP :=
n" can be used.
Additionally keep these disabled under CONFIG_COMPILE_TEST for now.
Link: https://github.com/KSPP/linux/issues/26 [1]
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hao Luo <haoluo@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
160 lines
3.1 KiB
C
160 lines
3.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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typedef void(*test_ubsan_fp)(void);
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#define UBSAN_TEST(config, ...) do { \
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pr_info("%s " __VA_ARGS__ "%s(%s=%s)\n", __func__, \
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sizeof(" " __VA_ARGS__) > 2 ? " " : "", \
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#config, IS_ENABLED(config) ? "y" : "n"); \
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} while (0)
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static void test_ubsan_add_overflow(void)
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{
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volatile int val = INT_MAX;
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UBSAN_TEST(CONFIG_UBSAN_SIGNED_WRAP);
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val += 2;
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}
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static void test_ubsan_sub_overflow(void)
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{
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volatile int val = INT_MIN;
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volatile int val2 = 2;
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UBSAN_TEST(CONFIG_UBSAN_SIGNED_WRAP);
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val -= val2;
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}
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static void test_ubsan_mul_overflow(void)
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{
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volatile int val = INT_MAX / 2;
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UBSAN_TEST(CONFIG_UBSAN_SIGNED_WRAP);
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val *= 3;
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}
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static void test_ubsan_negate_overflow(void)
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{
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volatile int val = INT_MIN;
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UBSAN_TEST(CONFIG_UBSAN_SIGNED_WRAP);
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val = -val;
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}
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static void test_ubsan_divrem_overflow(void)
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{
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volatile int val = 16;
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volatile int val2 = 0;
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UBSAN_TEST(CONFIG_UBSAN_DIV_ZERO);
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val /= val2;
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}
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static void test_ubsan_shift_out_of_bounds(void)
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{
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volatile int neg = -1, wrap = 4;
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volatile int val1 = 10;
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volatile int val2 = INT_MAX;
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UBSAN_TEST(CONFIG_UBSAN_SHIFT, "negative exponent");
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val1 <<= neg;
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UBSAN_TEST(CONFIG_UBSAN_SHIFT, "left overflow");
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val2 <<= wrap;
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}
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static void test_ubsan_out_of_bounds(void)
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{
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volatile int i = 4, j = 5, k = -1;
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volatile char above[4] = { }; /* Protect surrounding memory. */
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volatile int arr[4];
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volatile char below[4] = { }; /* Protect surrounding memory. */
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above[0] = below[0];
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UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "above");
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arr[j] = i;
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UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "below");
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arr[k] = i;
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}
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enum ubsan_test_enum {
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UBSAN_TEST_ZERO = 0,
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UBSAN_TEST_ONE,
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UBSAN_TEST_MAX,
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};
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static void test_ubsan_load_invalid_value(void)
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{
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volatile char *dst, *src;
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bool val, val2, *ptr;
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enum ubsan_test_enum eval, eval2, *eptr;
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unsigned char c = 0xff;
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UBSAN_TEST(CONFIG_UBSAN_BOOL, "bool");
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dst = (char *)&val;
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src = &c;
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*dst = *src;
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ptr = &val2;
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val2 = val;
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UBSAN_TEST(CONFIG_UBSAN_ENUM, "enum");
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dst = (char *)&eval;
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src = &c;
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*dst = *src;
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eptr = &eval2;
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eval2 = eval;
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}
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static void test_ubsan_misaligned_access(void)
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{
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volatile char arr[5] __aligned(4) = {1, 2, 3, 4, 5};
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volatile int *ptr, val = 6;
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UBSAN_TEST(CONFIG_UBSAN_ALIGNMENT);
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ptr = (int *)(arr + 1);
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*ptr = val;
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}
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static const test_ubsan_fp test_ubsan_array[] = {
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test_ubsan_add_overflow,
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test_ubsan_sub_overflow,
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test_ubsan_mul_overflow,
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test_ubsan_negate_overflow,
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test_ubsan_shift_out_of_bounds,
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test_ubsan_out_of_bounds,
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test_ubsan_load_invalid_value,
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test_ubsan_misaligned_access,
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};
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/* Excluded because they Oops the module. */
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static const test_ubsan_fp skip_ubsan_array[] = {
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test_ubsan_divrem_overflow,
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};
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static int __init test_ubsan_init(void)
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{
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unsigned int i;
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for (i = 0; i < ARRAY_SIZE(test_ubsan_array); i++)
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test_ubsan_array[i]();
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return 0;
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}
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module_init(test_ubsan_init);
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static void __exit test_ubsan_exit(void)
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{
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/* do nothing */
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}
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module_exit(test_ubsan_exit);
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MODULE_AUTHOR("Jinbum Park <jinb.park7@gmail.com>");
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MODULE_LICENSE("GPL v2");
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