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

Paul B Mahol onemda at gmail.com
Mon Jan 7 21:51:33 EET 2019


On 1/7/19, https://ieeexplore.ieee.org/document/7291728Michael
Niedermayer <michael at niedermayer.cc> wrote:
> On Mon, Jan 07, 2019 at 07:41:04PM +0100, Paul B Mahol wrote:
>> 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
>> >
>> > _______________________________________________
>> > ffmpeg-devel mailing list
>> > ffmpeg-devel at ffmpeg.org
>> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>> >
>>
>> lgtm if output does not change.
>
> fate-qpeg passes and it executes this codepath
> do you have any other files i should test ?
>

look in samples.ffmpeg.org ?

> thx
>
>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Good people do not need laws to tell them to act responsibly, while bad
> people will find a way around the laws. -- Plato
>


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