[FFmpeg-devel] [PATCH 09/12] avcodec/pafvideo: Only clear frame when it was written to

[Paul B Mahol]

Why this does not set dirty for all decoding cases?

On 9/25/19, Michael Niedermayer <michael at niedermayer.cc> wrote:
> This avoids unneeded operations and makes the code faster.
>
> Fixes: Timeout
> Fixes:
> 15724/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PAF_VIDEO_fuzzer-5750842205929472
> (12sec -> 9sec)
> Fixes:
> 17625/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PAF_VIDEO_fuzzer-5640515311108096
> (16sec -> 4sec)
>
> 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/pafvideo.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/libavcodec/pafvideo.c b/libavcodec/pafvideo.c
> index 6b4771cbce..07fa05caf8 100644
> --- a/libavcodec/pafvideo.c
> +++ b/libavcodec/pafvideo.c
> @@ -55,6 +55,7 @@ typedef struct PAFVideoDecContext {
>
>      int current_frame;
>      uint8_t *frame[4];
> +    int dirty[4];
>      int frame_size;
>      int video_size;
>
> @@ -187,6 +188,7 @@ static int decode_0(PAFVideoDecContext *c, uint8_t *pkt,
> uint8_t code)
>              j      = bytestream2_get_le16(&c->gb) + offset;
>              if (bytestream2_get_bytes_left(&c->gb) < (j - offset) * 16)
>                  return AVERROR_INVALIDDATA;
> +            c->dirty[page] = 1;
>              do {
>                  offset++;
>                  if (dst + 3 * c->width + 4 > dend)
> @@ -329,9 +331,13 @@ static int paf_video_decode(AVCodecContext *avctx, void
> *data,
>          c->pic->palette_has_changed = 1;
>      }
>
> +    c->dirty[c->current_frame] = 1;
>      if (code & 0x20)
> -        for (i = 0; i < 4; i++)
> -            memset(c->frame[i], 0, c->frame_size);
> +        for (i = 0; i < 4; i++) {
> +            if (c->dirty[i])
> +                memset(c->frame[i], 0, c->frame_size);
> +            c->dirty[i] = 0;
> +        }
>
>      switch (code & 0x0F) {
>      case 0:
> --
> 2.23.0
>
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