[FFmpeg-devel] [PATCH 1/5] avcodec/binkaudio: Check sample rate

[Peter Ross]

On Sat, Oct 12, 2019 at 06:53:05PM -0300, James Almer wrote:
> On 10/12/2019 5:47 PM, Michael Niedermayer wrote:
> > On Fri, Oct 11, 2019 at 08:51:54PM +1100, Peter Ross wrote:
> >> On Fri, Oct 11, 2019 at 12:40:07AM +0200, Michael Niedermayer wrote:
> >>> Fixes: signed integer overflow: 1092624416 * 2 cannot be represented in type 'int'
> >>> Fixes: 18045/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_BINKAUDIO_RDFT_fuzzer-5718519492116480
> >>>
> >>> 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/binkaudio.c | 2 ++
> >>>  1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/libavcodec/binkaudio.c b/libavcodec/binkaudio.c
> >>> index 96cf968c66..2384ebf312 100644
> >>> --- a/libavcodec/binkaudio.c
> >>> +++ b/libavcodec/binkaudio.c
> >>> @@ -95,6 +95,8 @@ static av_cold int decode_init(AVCodecContext *avctx)
> >>>      if (avctx->codec->id == AV_CODEC_ID_BINKAUDIO_RDFT) {
> >>>          // audio is already interleaved for the RDFT format variant
> >>>          avctx->sample_fmt = AV_SAMPLE_FMT_FLT;
> >>> +        if (sample_rate > INT_MAX / avctx->channels)
> >>> +            return AVERROR_INVALIDDATA;
> >>>          sample_rate  *= avctx->channels;
> >>>          s->channels = 1;
> >>>          if (!s->version_b)
> >>> -- 
> >>> 2.23.0
> >>
> >> i think this checl belongs inside the fuzzer test harness, or as a general
> >> purpose codec check.
> >>
> >> the bink and smaker demuxers will only ever use BINKAUDIO_RDFT with 1 or 2 channels.
> > 
> > In the case of the overflow channels was 2
> > 
> > what check do you suggest to be done in general code ?
> > A check specific to the fuzzer would fail to prevent this from happening
> > outside the fuzzer

fair enough, approve patch.

> Judging by the bink demuxer reading 16 bits for sample_rate, I assume
> binkaudio has a max valid value for it, like 44k or 48k, in which case a
> check like the one for channels at the beginning of this function would
> be the proper non general code fix. If not one of those two values, then
> just <= UINT16_MAX.

the bink demuxer supplied sample_reate is 16-bits wide, smacker is 24-bits.
the error can never happen when using ffmpeg+libavformat+libavcodec to play any
bink or smacker files, but i guess we need to account for other use cases.

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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