[vlc-devel] [vlc-commits] demux: av1_unpack: fix leb128 width estimation

[Steve Lhomme]

On 12/10/2018 09:26, Francois Cartegnie wrote:
> Le 12/10/2018 à 08:29, Steve Lhomme a écrit :
>
>>> diff --git a/modules/demux/av1_unpack.h b/modules/demux/av1_unpack.h
>>> index 683c53423d..af7f056abf 100644
>>> --- a/modules/demux/av1_unpack.h
>>> +++ b/modules/demux/av1_unpack.h
>>> @@ -26,10 +26,10 @@
>>>      static inline uint8_t leb128_expected(uint32_t v)
>> Shouldn't this be at least 64 bits ?
> We're not supposed to write numbers > 32bits.
>
>>>    {
>>> -    if     (v < (1U << 8))  return 1;
>>> -    else if(v < (1U << 15)) return 2;
>>> -    else if(v < (1U << 22)) return 3;
>>> -    else if(v < (1U << 29)) return 4;
>>> +    if     (v < (1U << 7))  return 1;
>>> +    else if(v < (1U << 14)) return 2;
>>> +    else if(v < (1U << 21)) return 3;
>>> +    else if(v < (1U << 28)) return 4;
>> And test all the way to the amount of bits we have. Malformed files will
>> exist (also, fuzzer).
> That's writer, not reader.

Ah, I missed that part.

> It only depends on leading zeroes and we never provide > 32bits.
>
>
> -- 
> Francois Cartegnie
> VideoLAN - VLC Developer
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