[FFmpeg-devel] [PATCHv4] VP4 video decoder

[Reimar Döffinger]

On Tue, May 21, 2019 at 11:15:03AM -0300, James Almer wrote:
> > I have a feeling this loop should have a stop condition like v <
> > SOME_LARGE_VALUE, say INT_MAX-255 or yuv_macroblock_count, to reject
> > corrupt/malicious files and not cause undefined behavior
>
> Using get_bits_left(gb) would be better than an arbitrary large value.

It seems the original comment wasn't preserved, but get_bits_left
is fairly pointless because the 0-padding will cause loop exit
anyway.
Also get_bits_left wouldn't address the point that a 2GB input frame
of all-1s from the right position would here end up reading 2GB
9 bits at a time.
Overflow by my calculations would only happen after > 500 GB,
so not sure that's a worry.
But depending on the contexts in which this function is used,
there might be obvious limits for v, in which case an early
exit would make sense (even when not, runs > 250 bytes can
likely safely assumed broken).