[FFmpeg-devel] [PATCH] lavfi/avfiltergraph: always reduce all_layouts to a single layout

[Marton Balint]

On Wed, 23 Nov 2016, Nicolas George wrote:

> Le duodi 2 frimaire, an CCXXV, Marton Balint a écrit :
>> Wouldn't it make sense to change the default to allow unknown channel
>> layouts as well, if no query_formats is specified?
>
> Only if you volunteer to monitor all merges from the fork to check that
> they work with unknown layouts.
>
> Because that is the issue; filters from the fork that need the number of
> channels get it from the channel layout, and if a filter uses the
> invalid number of channels it may cause crashes, possibly exploitable.

I thought we are trying to move away from workarounds introduced only to 
be able to be compatible with libav API. So this is clearly libav dirving 
ffmpeg development, which is not fortunate IMHO.

I also think that the chance of an exploitable filter because of this 
is small. An audio filter with no query_formats is quite rare in itself. 
Even if such a filter got merged, making it work with unknown channel 
layouts is a feature which we would want anyway, becase ffmpeg does 
support unknown channel layouts.

Yes, it is not me who does the merges, but IMHO this does not add too 
much burden for the people who does it. Hendrik, Clement, what do you 
think?

And even if such an issue got in the codebase, isn't this something that 
coverity should be able to easily detect most of the times?

Thanks,
Marton