On Mon, Dec 06, 2021 at 07:01:24PM +0100, Andreas Rheinhardt wrote: > Michael Niedermayer: > > Fixes: OOM > > Fixes: > > 41595/clusterfuzz-testcase-minimized-ffmpeg_dem_FOURXM_fuzzer-6355979363549184 > > > > Found-by: continuous fuzzing process > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > --- > > libavformat/4xm.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/libavformat/4xm.c b/libavformat/4xm.c > > index f918b1fc572..5cbae7053d8 100644 > > --- a/libavformat/4xm.c > > +++ b/libavformat/4xm.c > > @@ -137,7 +137,8 @@ static int parse_strk(AVFormatContext *s, > > return AVERROR_INVALIDDATA; > > > > track = AV_RL32(buf + 8); > > - if ((unsigned)track >= UINT_MAX / sizeof(AudioTrack) - 1) { > > + if ((unsigned)track >= UINT_MAX / sizeof(AudioTrack) - 1 || > > + s->max_streams && track >= s->max_streams) { > > av_log(s, AV_LOG_ERROR, "current_track too large\n"); > > return AVERROR_INVALIDDATA; > > } > > > > Why do you treat s->max_streams == 0 as "no limit on the number of > streams"? Neither the documentation nor avformat_new_stream() treat it > as such.
0 was used as no limit in other cases, i did not check nor remembered that AVFormatContext.max_streams doesnt have 0 as a documented exception i will remove the 0 check > I think a better way to fix this is to stop allocating based upon track > and rather allocate based upon the actual number of tracks seen (so > AudioTrack needs to have a track field, but the stream_index field could > be dropped). > Also notice that this demuxer currently doesn't check that the track ids will add that > encountered are unique. As a result, there can be multiple AVStreams > with the same id, only the last of which will return packets. > Another way to limit allocations of this demuxer is to not read the > whole file header into memory. Most of these files have 1 stream and an id of 0. I have found 1 file which has 7 streams, with id 0,1,2,3,4,5,6 in that order IIRC so it feels a bit overkillish to remap this around, but i surely see your argument behind this thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In a rich man's house there is no place to spit but his face. -- Diogenes of Sinope
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