[FFmpeg-devel] [PATCH 1/3] 4xm: prevent overflow during bit rate calculation

[Andreas Cadhalpun]

On 16.12.2016 02:29, Rodger Combs wrote: 
>> On Dec 15, 2016, at 19:21, Andreas Cadhalpun <andreas.cadhalpun at googlemail.com> wrote:
>> On 15.12.2016 14:02, Ronald S. Bultje wrote:
>>> - if for whatever reason some things cannot be done in generic code or by
>>> changing the type (this should really cover most cases), and we want
>>> specific overflow checks, then maybe we want to have some generic helper
>>> macros that make them one-liners in decoders. This would return an error
>>> along with fixing the UB.
>>
>> I don't think the number of overflow checks added justifies the additional
>> complexity of factoring things out. These checks are also subtly different,
>> so it's not easy to write a generic helper for that.
>> However, I plan to do this for the actually common cases when validating
>> codec parameters, like checking that a parameter is not negative.
>>
> 
> My proposal was for something like:
> #define BAIL_ON_OVERFLOW(x) if (x) {av_log(avctx, AV_LOG_ERROR, "Overflow check failed: " #x); return AVERROR_INVALIDDATA;}
> Which basically reduces the code overhead down to a simple one-liner.

Yeah, that's similar to how I plan to handle the more common cases.

> It's hard to get detailed error prints out of this, but if we're saying these
> cases are so unlikely (fuzzer-only?) that we're comfortable outright failing
> on them, the level of precision in the message probably doesn't matter much?

Agreed, so I've updated the patch series using this approach.

Best regards,
Andreas