On Fri, Nov 22, 2019 at 07:20:55PM +0800, Limin Wang wrote: > On Thu, Nov 21, 2019 at 11:26:12PM +0100, Michael Niedermayer wrote: > > Fixes: signed integer overflow: -2147483648 - 13 cannot be represented in > > type 'int' > > Fixes: > > 18893/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ADPCM_IMA_APC_fuzzer-5630760442920960 > > > > Found-by: continuous fuzzing process > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > --- > > libavcodec/adpcm.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/libavcodec/adpcm.c b/libavcodec/adpcm.c > > index edf7052636..d3919288b1 100644 > > --- a/libavcodec/adpcm.c > > +++ b/libavcodec/adpcm.c > > @@ -140,8 +140,8 @@ static av_cold int adpcm_decode_init(AVCodecContext * > > avctx) > > break; > > case AV_CODEC_ID_ADPCM_IMA_APC: > > if (avctx->extradata && avctx->extradata_size >= 8) { > > - c->status[0].predictor = AV_RL32(avctx->extradata); > > - c->status[1].predictor = AV_RL32(avctx->extradata + 4); > > + c->status[0].predictor = > > av_clip_intp2(AV_RL32(avctx->extradata ), 18); > > + c->status[1].predictor = > > av_clip_intp2(AV_RL32(avctx->extradata + 4), 18); > > 18 is 16?
18 > I understand c->status[i].predictor is 16bit. ADPCMChannelStatus.predictor is an int so 32bit the place where predictor is used is adpcm_ima_expand_nibble() there its added to diff diff is maximally 32767*15 / 8 = 61438 if now predictor was -70000 then we would get -8562 if predictor was cliped to 16bit (-32768) would produce 28670 thats different. Same for 17bit which is why i choose 18. Its the smallest that does not change the output in any case. Also i dont see any cliping of the global header values in https://wiki.multimedia.cx/index.php/CRYO_APC thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB I have often repented speaking, but never of holding my tongue. -- Xenocrates
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