diff mbox series

[v2,2/3] test_overflow: Add shift overflow tests

Message ID 20180801000039.44314-3-keescook@chromium.org (mailing list archive)
State Superseded
Headers show
Series overflow.h: Add arithmetic shift helper | expand

Commit Message

Kees Cook Aug. 1, 2018, midnight UTC 
This adds overflow tests for the new check_shift_overflow() helper to
validate overflow, signedness glitches, storage glitches, etc.

Co-developed-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 lib/test_overflow.c | 140 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 139 insertions(+), 1 deletion(-)

Comments

Jason Gunthorpe Aug. 1, 2018, 2:13 a.m. UTC | #1 
On Tue, Jul 31, 2018 at 05:00:38PM -0700, Kees Cook wrote:
> +	/* Overflow: high bit falls off. */
> +	/* 10010110 */
> +	err |= TEST_ONE_SHIFT(150, 1, u8, 0, true);
> +	/* 1000100010010110 */
> +	err |= TEST_ONE_SHIFT(34966, 1, u16, 0, true);
> +	/* 10000100000010001000100010010110 */
> +	err |= TEST_ONE_SHIFT(2215151766U, 1, u32, 0, true);
> +	err |= TEST_ONE_SHIFT(2215151766U, 1, unsigned int, 0, true);
> +	/* 1000001000010000010000000100000010000100000010001000100010010110 */
> +	err |= TEST_ONE_SHIFT(9372061470395238550ULL, 1, u64, 0, true);

This same idea should be repeated with signed outputs and check both
overflow past the end (<<2) and overflow into the signed bit (<<1)

        /* Overflow, high bit falls into the sign bit or off the end */
	/* 01001011 */
	err |= TEST_ONE_SHIFT(75, 1, s8, 0, true);
	err |= TEST_ONE_SHIFT(75, 2, s8, 0, true);

And also general type mismatch overflow:

	err |= TEST_ONE_SHIFT(0x100, 0, u8, 0, true);
	err |= TEST_ONE_SHIFT(0xFF, 0, s8, 0, true);

Thanks,
Jason
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Kees Cook Aug. 1, 2018, 5:51 a.m. UTC | #2 
On Tue, Jul 31, 2018 at 7:13 PM, Jason Gunthorpe <jgg@ziepe.ca> wrote:
> On Tue, Jul 31, 2018 at 05:00:38PM -0700, Kees Cook wrote:
>> +     /* Overflow: high bit falls off. */
>> +     /* 10010110 */
>> +     err |= TEST_ONE_SHIFT(150, 1, u8, 0, true);
>> +     /* 1000100010010110 */
>> +     err |= TEST_ONE_SHIFT(34966, 1, u16, 0, true);
>> +     /* 10000100000010001000100010010110 */
>> +     err |= TEST_ONE_SHIFT(2215151766U, 1, u32, 0, true);
>> +     err |= TEST_ONE_SHIFT(2215151766U, 1, unsigned int, 0, true);
>> +     /* 1000001000010000010000000100000010000100000010001000100010010110 */
>> +     err |= TEST_ONE_SHIFT(9372061470395238550ULL, 1, u64, 0, true);
>
> This same idea should be repeated with signed outputs and check both
> overflow past the end (<<2) and overflow into the signed bit (<<1)
>
>         /* Overflow, high bit falls into the sign bit or off the end */
>         /* 01001011 */
>         err |= TEST_ONE_SHIFT(75, 1, s8, 0, true);
>         err |= TEST_ONE_SHIFT(75, 2, s8, 0, true);
>
> And also general type mismatch overflow:
>
>         err |= TEST_ONE_SHIFT(0x100, 0, u8, 0, true);
>         err |= TEST_ONE_SHIFT(0xFF, 0, s8, 0, true);

Ah yes, thanks. I've added these for the next version now.

-Kees
diff mbox series

Patch

diff --git a/lib/test_overflow.c b/lib/test_overflow.c
index 2278fe05a1b0..face66e8aa37 100644
--- a/lib/test_overflow.c
+++ b/lib/test_overflow.c
@@ -252,7 +252,8 @@  static int __init test_ ## t ## _overflow(void) {			\
 	int err = 0;							\
 	unsigned i;							\
 									\
-	pr_info("%-3s: %zu tests\n", #t, ARRAY_SIZE(t ## _tests));	\
+	pr_info("%-3s: %zu arithmetic tests\n", #t,			\
+		ARRAY_SIZE(t ## _tests));				\
 	for (i = 0; i < ARRAY_SIZE(t ## _tests); ++i)			\
 		err |= do_test_ ## t(&t ## _tests[i]);			\
 	return err;							\
@@ -287,6 +288,142 @@  static int __init test_overflow_calculation(void)
 	return err;
 }
 
+static int __init test_overflow_shift(void)
+{
+	int err = 0;
+
+/* Args are: value, shift, type, expected result, overflow expected */
+#define TEST_ONE_SHIFT(a, s, t, expect, of) ({				\
+	int __failed = 0;						\
+	typeof(a) __a = (a);						\
+	typeof(s) __s = (s);						\
+	t __e = (expect);						\
+	t __d;								\
+	bool __of = check_shift_overflow(__a, __s, &__d);		\
+	if (__of != of) {						\
+		pr_warn("expected (%s)(%s << %s) to%s overflow\n",	\
+			#t, #a, #s, of ? "" : " not");			\
+		__failed = 1;						\
+	} else if (!__of && __d != __e) {				\
+		pr_warn("expected (%s)(%s << %s) == %s\n",		\
+			#t, #a, #s, #expect);				\
+		if ((t)-1 < 0)						\
+			pr_warn("got %lld\n", (s64)__d);		\
+		else							\
+			pr_warn("got %llu\n", (u64)__d);		\
+		__failed = 1;						\
+	}								\
+	if (!__failed)							\
+		pr_info("ok: (%s)(%s << %s) == %s\n", #t, #a, #s,	\
+			of ? "overflow" : #expect);			\
+	__failed;							\
+})
+
+	/* Sane shifts */
+	err |= TEST_ONE_SHIFT(1, 4, u8, 1 << 4, false);
+	err |= TEST_ONE_SHIFT(1, 7, u8, 1 << 7, false);
+	err |= TEST_ONE_SHIFT(1, 10, u16, 1 << 10, false);
+	err |= TEST_ONE_SHIFT(1, 15, u16, 1 << 15, false);
+	err |= TEST_ONE_SHIFT(1, 30, int, 1 << 30, false);
+	err |= TEST_ONE_SHIFT(1, 30, s32, 1 << 30, false);
+	err |= TEST_ONE_SHIFT(1, 20, unsigned int, 1U << 20, false);
+	err |= TEST_ONE_SHIFT(1, 31, unsigned int, 1U << 31, false);
+	err |= TEST_ONE_SHIFT(1, 20, u32, 1U << 20, false);
+	err |= TEST_ONE_SHIFT(1, 31, u32, 1U << 31, false);
+	err |= TEST_ONE_SHIFT(1, 40, u64, 1ULL << 40, false);
+	err |= TEST_ONE_SHIFT(1, 63, u64, 1ULL << 63, false);
+
+	/* Sane shift: start and end with 0, without a too-wide shift. */
+	err |= TEST_ONE_SHIFT(0, 7, u8, 0, false);
+	err |= TEST_ONE_SHIFT(0, 15, u16, 0, false);
+	err |= TEST_ONE_SHIFT(0, 31, unsigned int, 0, false);
+	err |= TEST_ONE_SHIFT(0, 31, u32, 0, false);
+	err |= TEST_ONE_SHIFT(0, 63, u64, 0, false);
+
+	/* Sane shift: start and end with 0, without reaching signed bit. */
+	err |= TEST_ONE_SHIFT(0, 6, s8, 0, false);
+	err |= TEST_ONE_SHIFT(0, 14, s16, 0, false);
+	err |= TEST_ONE_SHIFT(0, 30, int, 0, false);
+	err |= TEST_ONE_SHIFT(0, 30, s32, 0, false);
+	err |= TEST_ONE_SHIFT(0, 62, s64, 0, false);
+
+	/* Overflow: shifted the bit off the end. */
+	err |= TEST_ONE_SHIFT(1, 8, u8, 0, true);
+	err |= TEST_ONE_SHIFT(1, 16, u16, 0, true);
+	err |= TEST_ONE_SHIFT(1, 32, unsigned int, 0, true);
+	err |= TEST_ONE_SHIFT(1, 32, u32, 0, true);
+	err |= TEST_ONE_SHIFT(1, 64, u64, 0, true);
+
+	/* Overflow: high bit falls off. */
+	/* 10010110 */
+	err |= TEST_ONE_SHIFT(150, 1, u8, 0, true);
+	/* 1000100010010110 */
+	err |= TEST_ONE_SHIFT(34966, 1, u16, 0, true);
+	/* 10000100000010001000100010010110 */
+	err |= TEST_ONE_SHIFT(2215151766U, 1, u32, 0, true);
+	err |= TEST_ONE_SHIFT(2215151766U, 1, unsigned int, 0, true);
+	/* 1000001000010000010000000100000010000100000010001000100010010110 */
+	err |= TEST_ONE_SHIFT(9372061470395238550ULL, 1, u64, 0, true);
+
+	/* Nonsense: negative initial value. */
+	err |= TEST_ONE_SHIFT(-1, 0, s8, 0, true);
+	err |= TEST_ONE_SHIFT(-5, 0, s16, 0, true);
+	err |= TEST_ONE_SHIFT(-10, 0, int, 0, true);
+	err |= TEST_ONE_SHIFT(-100, 0, s32, 0, true);
+	err |= TEST_ONE_SHIFT(-10000, 0, s64, 0, true);
+
+	/* Nonsense: negative shift values. */
+	err |= TEST_ONE_SHIFT(0, -5, s8, 0, true);
+	err |= TEST_ONE_SHIFT(0, -10, s16, 0, true);
+	err |= TEST_ONE_SHIFT(0, -15, int, 0, true);
+	err |= TEST_ONE_SHIFT(0, -20, s32, 0, true);
+	err |= TEST_ONE_SHIFT(0, -30, s64, 0, true);
+
+	/* Overflow: shifted at or beyond entire type's bit width. */
+	err |= TEST_ONE_SHIFT(0, 8, u8, 0, true);
+	err |= TEST_ONE_SHIFT(0, 9, u8, 0, true);
+	err |= TEST_ONE_SHIFT(0, 8, s8, 0, true);
+	err |= TEST_ONE_SHIFT(0, 9, s8, 0, true);
+	err |= TEST_ONE_SHIFT(0, 16, u16, 0, true);
+	err |= TEST_ONE_SHIFT(0, 17, u16, 0, true);
+	err |= TEST_ONE_SHIFT(0, 16, s16, 0, true);
+	err |= TEST_ONE_SHIFT(0, 17, s16, 0, true);
+	err |= TEST_ONE_SHIFT(0, 32, u32, 0, true);
+	err |= TEST_ONE_SHIFT(0, 33, u32, 0, true);
+	err |= TEST_ONE_SHIFT(0, 32, int, 0, true);
+	err |= TEST_ONE_SHIFT(0, 33, int, 0, true);
+	err |= TEST_ONE_SHIFT(0, 32, s32, 0, true);
+	err |= TEST_ONE_SHIFT(0, 33, s32, 0, true);
+	err |= TEST_ONE_SHIFT(0, 64, u64, 0, true);
+	err |= TEST_ONE_SHIFT(0, 65, u64, 0, true);
+	err |= TEST_ONE_SHIFT(0, 64, s64, 0, true);
+	err |= TEST_ONE_SHIFT(0, 65, s64, 0, true);
+
+	/* Overflow: shifted into signed bit. */
+	err |= TEST_ONE_SHIFT(1, 7, s8, 0, true);
+	err |= TEST_ONE_SHIFT(1, 15, s16, 0, true);
+	err |= TEST_ONE_SHIFT(1, 31, int, 0, true);
+	err |= TEST_ONE_SHIFT(1, 31, s32, 0, true);
+	err |= TEST_ONE_SHIFT(1, 63, s64, 0, true);
+
+	/*
+	 * Corner case: for unsigned types, we fail when we've shifted
+	 * through the entire width of bits. For signed types, we might
+	 * want to match this behavior, but that would mean noticing if
+	 * we shift through all but the signed bit, and this is not
+	 * currently detected (but we'll notice an overflow into the
+	 * signed bit). So, for now, we will test this condition but
+	 * mark it as not expected to overflow.
+	 */
+	err |= TEST_ONE_SHIFT(0, 7, s8, 0, false);
+	err |= TEST_ONE_SHIFT(0, 15, s16, 0, false);
+	err |= TEST_ONE_SHIFT(0, 31, int, 0, false);
+	err |= TEST_ONE_SHIFT(0, 31, s32, 0, false);
+	err |= TEST_ONE_SHIFT(0, 63, s64, 0, false);
+
+	return err;
+}
+
 /*
  * Deal with the various forms of allocator arguments. See comments above
  * the DEFINE_TEST_ALLOC() instances for mapping of the "bits".
@@ -397,6 +534,7 @@  static int __init test_module_init(void)
 	int err = 0;
 
 	err |= test_overflow_calculation();
+	err |= test_overflow_shift();
 	err |= test_overflow_allocation();
 
 	if (err) {