On Sat, Oct 03, 2020 at 10:43:04AM +0200, Paul B Mahol wrote: > On Fri, Oct 02, 2020 at 11:07:09PM +0200, Michael Niedermayer wrote: > > The MV checks did not consider the width and height of the block, also they > > had some off by 1 errors. This resulted in undefined behavior and crashes. > > This commit instead errors out on these > > > > Fixes: out of array read > > Fixes: > > 26080/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MOBICLIP_fuzzer-5758146355920896 > > > > Found-by: continuous fuzzing process > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > --- > > libavcodec/mobiclip.c | 30 ++++++------------------------ > > 1 file changed, 6 insertions(+), 24 deletions(-) > > > > diff --git a/libavcodec/mobiclip.c b/libavcodec/mobiclip.c > > index f890cb2599..a03ef8fb7d 100644 > > --- a/libavcodec/mobiclip.c > > +++ b/libavcodec/mobiclip.c > > @@ -1189,14 +1189,14 @@ static int predict_motion(AVCodecContext *avctx, > > dst_linesize = s->pic[s->current_pic]->linesize[i]; > > dst = s->pic[s->current_pic]->data[i] + offsetx + offsety * > > dst_linesize; > > > > + if (offsetx + (mv.x >> 1) < 0 || > > + offsety + (mv.y >> 1) < 0 || > > + offsetx + width + (mv.x + 1 >> 1) > fwidth || > > + offsety + height + (mv.y + 1 >> 1) > fheight) > > + return AVERROR_INVALIDDATA; [...]
> > @@ -1243,12 +1231,6 @@ static int predict_motion(AVCodecContext *avctx, > > } > > break; > > case 3: > > - if (offsety + (mv.y >> 1) < 0 || > > - offsety + (mv.y >> 1) >= fheight - 1 || > > - offsetx + (mv.x >> 1) < 0 || > > - offsetx + (mv.x >> 1) >= fwidth) > > - return AVERROR_INVALIDDATA; > > - > > You completely ignore this case, here it need one scanline extra. case 3 implies method= 3 implies mv.y is odd which makes (mv.y + 1 >> 1) 1 larger and that makes the test require 1 line more thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB If you think the mosad wants you dead since a long time then you are either wrong or dead since a long time.
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