[FFmpeg-devel] [PATCH] avcodec/get_bits: don't shift more bits than available in an unsigned with get_leb()

[James Almer]

On 1/30/2024 7:19 PM, Andreas Rheinhardt wrote:
> James Almer:
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>   libavcodec/get_bits.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/get_bits.h b/libavcodec/get_bits.h
>> index 9e19d2a439..c0cc7c0a7d 100644
>> --- a/libavcodec/get_bits.h
>> +++ b/libavcodec/get_bits.h
>> @@ -725,7 +725,7 @@ static inline unsigned get_leb(GetBitContext *s) {
>>           int byte = get_bits(s, 8);
>>           unsigned bits = byte & 0x7f;
>>           more = byte & 0x80;
>> -        if (i <= 4)
>> +        if (i <= 3 || (i == 4 && bits < (1 << 4)))
>>               leb |= bits << (i * 7);
>>           if (++i == 8)
>>               break;
> 
> This truncates more bits than necessary, which is IMO against the
> documentation of this function.

Mmh, true. I'll just leave it as is then. So patch withdrawn.