[FFmpeg-devel] [PATCH 2/2] avcodec/pngdec: Check nb_blocks

[Paul B Mahol]

On 5/24/19, Michael Niedermayer <michael at niedermayer.cc> wrote:
> On Sun, Apr 28, 2019 at 12:37:12PM +0200, Paul B Mahol wrote:
>> On 4/28/19, Michael Niedermayer <michael at niedermayer.cc> wrote:
>> > Fixes: Timeout (23sec -> 0.5sec)
>> > Fixes:
>> > 14329/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_LSCR_fuzzer-5679252923482112
>> >
>> > 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/pngdec.c | 2 ++
>> >  1 file changed, 2 insertions(+)
>> >
>> > diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
>> > index 6a681be29d..1dcde6cbc9 100644
>> > --- a/libavcodec/pngdec.c
>> > +++ b/libavcodec/pngdec.c
>> > @@ -1541,6 +1541,8 @@ static int decode_frame_lscr(AVCodecContext
>> > *avctx,
>> >          return ret;
>> >
>> >      nb_blocks = bytestream2_get_le16(gb);
>> > +    if (2 + nb_blocks * 12 > bytestream2_get_bytes_left(gb))
>>
>> I prefer if this is not reversed.
>
> of course, will unreverse and push as "if (bytestream2_get_bytes_left(gb) <
> 2 + nb_blocks * 12)"
>
> thanks


OK.