On Sun, Dec 13, 2020 at 07:12:29AM +1100, Peter Ross wrote: > On Sat, Dec 12, 2020 at 12:38:43PM +0100, Michael Niedermayer wrote: > > Fixes: infinite loop > > Fixes: > > 28042/clusterfuzz-testcase-minimized-ffmpeg_dem_WTV_fuzzer-6311288967528448 > > > > Found-by: continuous fuzzing process > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > --- > > libavformat/wtvdec.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/libavformat/wtvdec.c b/libavformat/wtvdec.c > > index 77908e6392..6c41e3c1a3 100644 > > --- a/libavformat/wtvdec.c > > +++ b/libavformat/wtvdec.c > > @@ -953,6 +953,9 @@ static int parse_chunks(AVFormatContext *s, int mode, > > int64_t seekts, int *len_p > > } else > > av_log(s, AV_LOG_WARNING, "unsupported chunk:"FF_PRI_GUID"\n", > > FF_ARG_GUID(g)); > > > > + if (avio_feof(pb)) > > + break; > > + > > avio_skip(pb, WTV_PAD8(len) - consumed); > > } > > return AVERROR_EOF; > > -- > > 2.17.1 > > curious how the infinte loop occurs here, as the while loop already tests > avio_feof(). > > i suspect it is because the fuzzed case results in 'consumed > len', and > therefore avio_skip is seeking backwards.
yes, WTV_PAD8(len) is 88 and consumed is 124 in the testcase, the eof flag is reset from the backward seek and so the other test doesnt trigger thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Those who are best at talking, realize last or never when they are wrong.
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