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

[Kees Cook]

On Tue, Jul 31, 2018 at 7:13 PM, Jason Gunthorpe <jgg@xxxxxxxx> 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

-- 
Kees Cook
Pixel Security