[FFmpeg-devel] [PATCH] avcodec/cbs_h2645: Check NAL space
James Almer
jamrial at gmail.com
Mon Apr 22 23:46:10 EEST 2024
On 4/22/2024 5:40 PM, Mark Thompson wrote:
> On 22/04/2024 02:31, Michael Niedermayer wrote:
>> Found-by-reviewing: CID1419833 Untrusted loop bound
>>
>> Sponsored-by: Sovereign Tech Fund
>> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
>> ---
>> libavcodec/cbs_h2645.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
>> index fe2e383ff33..1a45d424bae 100644
>> --- a/libavcodec/cbs_h2645.c
>> +++ b/libavcodec/cbs_h2645.c
>> @@ -709,7 +709,11 @@ static int cbs_h2645_split_fragment(CodedBitstreamContext *ctx,
>>
>> start = bytestream2_tell(&gbc);
>> for(i = 0; i < num_nalus; i++) {
>> + if (bytestream2_get_bytes_left(&gbc) < 2)
>> + return AVERROR_INVALIDDATA;
>> size = bytestream2_get_be16(&gbc);
>> + if (bytestream2_get_bytes_left(&gbc) < size)
>> + return AVERROR_INVALIDDATA;
>> bytestream2_skip(&gbc, size);
>> }
>> end = bytestream2_tell(&gbc);
>
> Seems fair.
>
> The problem looks more general with missing bounds checks in all the H.266 code around this, though? Compare with H.26[45], which have checks on all the reads - seems like H.266 should be doing that.
>
> Thanks,
Not against this approach, but since the bytestream2_get_* functions
return 0, never overread the buffer or move the internal pointer,
wouldn't it be enough to just ensure end > start?
Particularly in ff_h2645_packet_split(), we can return an error if
length (in this case being set to end - start) is < 4.
More information about the ffmpeg-devel
mailing list