[FFmpeg-devel] [PATCH 1/4] avformat/hlsenc: Fix extradata length check

[Steven Liu]

Andreas Rheinhardt <andreas.rheinhardt at gmail.com> 于2020年10月20日周二 下午7:03写道：
>
> Commit a2b1dd0ce301450a47c972745a6b33c4c273aa5d added support for
> parsing annex B HEVC extradata to extract profile and level information.
> Yet it only checks for there to be enough data left for the startcode
> and the first byte of the NAL unit header and not for the full NAL unit
> header; it simply presumes the second byte of the NAL unit header to be
> present and skips it. Then the remaining size of the extradata is calculated
> which ends up negative if the second byte of the NAL unit header is not
> present. Yet when calling ff_nal_unit_extract_rbsp() it
> will be converted to an uint32_t and end up as UINT32_MAX which
> will cause mayhem.
>
> This is solved by making sure that there is always enough remaining
> extradata that could (pending 0x03 escapes) contain the data that we
> are interested in.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
>  libavformat/hlsenc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> index 8e4cc36d50..49c4ab5966 100644
> --- a/libavformat/hlsenc.c
> +++ b/libavformat/hlsenc.c
> @@ -349,7 +349,7 @@ static void write_codec_attr(AVStream *st, VariantStream *vs)
>              level = st->codecpar->level;
>
>          /* check the boundary of data which from current position is small than extradata_size */
> -        while (data && (data - st->codecpar->extradata + 5) < st->codecpar->extradata_size) {
> +        while (data && (data - st->codecpar->extradata + 19) < st->codecpar->extradata_size) {
>              /* get HEVC SPS NAL and seek to profile_tier_level */
>              if (!(data[0] | data[1] | data[2]) && data[3] == 1 && ((data[4] & 0x42) == 0x42)) {
>                  int remain_size = 0;
> --
> 2.25.1
>
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LGTM

Thanks
Steven