[FFmpeg-devel] [PATCH] [h264] Use small padding with the checked bitstream reader.

[James Almer]

On 8/17/2024 3:04 PM, Michael Niedermayer wrote:
> On Wed, Aug 14, 2024 at 04:32:36PM -0700, Dale Curtis wrote:
>> MAX_MBPAIR_SIZE was added in 23f5cff92cdcfa55a735c458fcb5f95c0e0f3b1f
>> to prevent CABAC/CAVLC overread issues. It adds 256kb of padding to
>> RBSP allocations. AFAICT it seems unnecessary with the checked
>> bitstream reader. Dropping this padding is a substantial memory
>> improvement for constrained devices.
>>
>> 782865bf3094e36cbb4bd9cfacda252307e6589d removed the small padding
>> when AV_CODEC_FLAG2_FAST was set, but I don't have access to that
>> fuzzer test case to check this patch. Does anyone have this for testing?
> 
> 20978/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_H264_fuzzer-5746381832847360 sent privately
> 
> thx

Could the padding be changed to AV_INPUT_BUFFER_PADDING_SIZE instead of 
0 when small_padding is requested?