[FFmpeg-devel] [PATCH 4/5] avcodec/alac: Check for bps of 0

[Paul B Mahol]

On Mon, Aug 26, 2019 at 7:45 PM Baptiste Coudurier <
baptiste.coudurier at gmail.com> wrote:

> Hi Paul,
>
>
> > On Aug 25, 2019, at 12:37 AM, Paul B Mahol <onemda at gmail.com> wrote:
> >
> > On Sun, Aug 25, 2019 at 9:33 AM Michael Niedermayer
> <michael at niedermayer.cc>
> > wrote:
> >
> >> On Fri, Aug 23, 2019 at 11:20:48AM -0300, James Almer wrote:
> >>> On 8/8/2019 8:23 PM, Michael Niedermayer wrote:
> >>>> Fixes: shift exponent 32 is too large for 32-bit type 'unsigned int'
> >>>> Fixes:
> >>
> 15764/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALAC_fuzzer-5102101203517440
> >>>>
> >>>> 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/alac.c | 2 +-
> >>>> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/libavcodec/alac.c b/libavcodec/alac.c
> >>>> index 6086e2caa8..1196925aa7 100644
> >>>> --- a/libavcodec/alac.c
> >>>> +++ b/libavcodec/alac.c
> >>>> @@ -250,7 +250,7 @@ static int decode_element(AVCodecContext *avctx,
> >> AVFrame *frame, int ch_index,
> >>>>
> >>>>     alac->extra_bits = get_bits(&alac->gb, 2) << 3;
> >>>>     bps = alac->sample_size - alac->extra_bits + channels - 1;
> >>>> -    if (bps > 32U) {
> >>>> +    if (bps > 32 || bps < 1) {
> >>>>         avpriv_report_missing_feature(avctx, "bps %d", bps);
> >>>>         return AVERROR_PATCHWELCOME;
> >>>
> >>> bps 0 (or negative) is obviously a broken file,
> >>
> >> id say very likely a broken file, yes
> >>
> >>
> >>> so asking for a sample
> >>> is pointless. Just return invalid data in those cases, and leave this
> >>> check for > 32.
> >>
> >> thats a few lines more code, for an error code and different/no message
> >> its a bit difficult to guess where people prefer the extra code to be
> >> correct and where they prefer somewhat incorrect solutions to minimize
> >> fuzzer found bugfixes.
> >>
> >
> > If you dislike what people prefer when reviewing, perhaps you should stop
> > sending patches :-)
>
> This remark sounds rude and disrespectful to me.
> Please refrain from making remarks like this one in the future.
>

I do not see how this can be rude and disrespectful to you or anyone else.


>
> —
> Baptiste
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