[FFmpeg-devel] [PATCH] fate/integer.c: Connect test to fuzzer

[Michael Niedermayer]

On Sat, May 15, 2021 at 10:08:17PM +0530, Vedaa wrote:
> Hi,
> 
> Apologies for the trivial mistakes. I have fixed them in this patch.
> I have also added simple checks for overflow and underflow. Would this
> be sufficient or should I reduce the bits I read from the fuzzer?

its ok but theres a minor issue remaining


> I will also submit a pull request to oss-fuzz as soon as this patch is
> applied. :)

ok

[...]

> +int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
> +
> +int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
> +    if (size < 2 * sizeof(int64_t))
> +        return 1;
> +

> +    int64_t a,b,pdt;

This would produce a compiler warning 


> +    a = AV_RB64(data);
> +    b = AV_RB64(data + sizeof(int64_t));

> +    pdt = a * b;

Signed integer overflow is undefined behavior in C


> +    if ((b > 0 && a < INT64_MAX - b && a > INT64_MIN + b ) ||
> +        (b < 0 && a > INT64_MIN - b && a < INT64_MAX + b) &&
> +        pdt/b == a)
> +        TestInteger(a,b);
> +    return 0;
> +}

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Complexity theory is the science of finding the exact solution to an
approximation. Benchmarking OTOH is finding an approximation of the exact
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