[FFmpeg-devel] [PATCH] avcodec/qpeg: Optimize long runs in qpeg_decode_intra() not spanning a full row

[Paul B Mahol]

On 1/7/19, Michael Niedermayer <michael at niedermayer.cc> wrote:
> Fixes: Timeout
> Fixes:
> 11354/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_QPEG_fuzzer-5766275943366656
>
> Before: Executed
> clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_QPEG_fuzzer-5766275943366656
> in 9470 ms
> After : Executed
> clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_QPEG_fuzzer-5766275943366656
> in  134 ms
>
> Found-by: continuous fuzzing process
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/qpeg.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/qpeg.c b/libavcodec/qpeg.c
> index cb452621e7..654fd998d6 100644
> --- a/libavcodec/qpeg.c
> +++ b/libavcodec/qpeg.c
> @@ -80,7 +80,10 @@ static void qpeg_decode_intra(QpegContext *qctx, uint8_t
> *dst,
>
>              p = bytestream2_get_byte(&qctx->buffer);
>              for(i = 0; i < run; i++) {
> -                dst[filled++] = p;
> +                int step = FFMIN(run - i, width - filled);
> +                memset(dst+filled, p, step);
> +                filled += step;
> +                i      += step - 1;
>                  if (filled >= width) {
>                      filled = 0;
>                      dst -= stride;
> --
> 2.20.1
>
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>

lgtm if output does not change.