On Sun, Jun 16, 2019 at 08:31:37PM +0200, Lynne wrote: > Jun 16, 2019, 4:12 PM by one...@gmail.com: > > > On 6/16/19, Reimar Döffinger <reimar.doeffin...@gmx.de> wrote: > > > >> > >> > >> On 16.06.2019, at 12:30, Lynne <d...@lynne.ee> wrote: > >> > >>> Jun 16, 2019, 10:57 AM by mich...@niedermayer.cc: > >>> > >>>> Fixes: left shift of negative value -4 > >>>> Fixes: signed integer overflow: -15091694 * 167 cannot be represented in > >>>> type 'int' > >>>> Fixes: signed integer overflow: 1898547155 + 453967445 cannot be > >>>> represented in type 'int' > >>>> Fixes: > >>>> 15258/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APE_fuzzer-5759095564402688 > >>>> > >>>> Found-by: continuous fuzzing process > >>>> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > >>>> Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > >>>> --- > >>>> libavcodec/apedec.c | 16 ++++++++-------- > >>>> 1 file changed, 8 insertions(+), 8 deletions(-) > >>>> > >>>> diff --git a/libavcodec/apedec.c b/libavcodec/apedec.c > >>>> index 61ebfdafd5..f1bfc634c2 100644 > >>>> --- a/libavcodec/apedec.c > >>>> +++ b/libavcodec/apedec.c > >>>> @@ -859,22 +859,22 @@ static av_always_inline int > >>>> filter_3800(APEPredictor *p, > >>>> return predictionA; > >>>> } > >>>> d2 = p->buf[delayA]; > >>>> - d1 = (p->buf[delayA] - p->buf[delayA - 1]) << 1; > >>>> - d0 = p->buf[delayA] + ((p->buf[delayA - 2] - p->buf[delayA - 1]) << > >>>> 3); > >>>> + d1 = (p->buf[delayA] - p->buf[delayA - 1]) * 2; > >>>> + d0 = p->buf[delayA] + ((p->buf[delayA - 2] - p->buf[delayA - 1]) * > >>>> 8); > >>>> d3 = p->buf[delayB] * 2 - p->buf[delayB - 1]; > >>>> d4 = p->buf[delayB]; > >>>> > >>>> - predictionA = d0 * p->coeffsA[filter][0] + > >>>> - d1 * p->coeffsA[filter][1] + > >>>> - d2 * p->coeffsA[filter][2]; > >>>> + predictionA = d0 * (unsigned)p->coeffsA[filter][0] + > >>>> + d1 * (unsigned)p->coeffsA[filter][1] + > >>>> + d2 * (unsigned)p->coeffsA[filter][2]; > >>>> > >>>> sign = APESIGN(decoded); > >>>> p->coeffsA[filter][0] += (((d0 >> 30) & 2) - 1) * sign; > >>>> p->coeffsA[filter][1] += (((d1 >> 28) & 8) - 4) * sign; > >>>> p->coeffsA[filter][2] += (((d2 >> 28) & 8) - 4) * sign; > >>>> > >>>> - predictionB = d3 * p->coeffsB[filter][0] - > >>>> - d4 * p->coeffsB[filter][1]; > >>>> + predictionB = d3 * (unsigned)p->coeffsB[filter][0] - > >>>> + d4 * (unsigned)p->coeffsB[filter][1]; > >>>> p->lastA[filter] = decoded + (predictionA >> 11); > >>>> sign = APESIGN(p->lastA[filter]); > >>>> p->coeffsB[filter][0] += (((d3 >> 29) & 4) - 2) * sign; > >>>> @@ -902,7 +902,7 @@ static void long_filter_high_3800(int32_t *buffer, > >>>> int order, int shift, int len > >>>> dotprod = 0; > >>>> sign = APESIGN(buffer[i]); > >>>> for (j = 0; j < order; j++) { > >>>> - dotprod += delay[j] * coeffs[j]; > >>>> + dotprod += delay[j] * (unsigned)coeffs[j]; > >>>> coeffs[j] += ((delay[j] >> 31) | 1) * sign; > >>>> } > >>>> buffer[i] -= dotprod >> shift; > >>>> > >>> > >>> This code is DSP, overflows should be allowed in case input is corrupt. > >>> > >> > >> Then get the C standard changed or use a different language. > >> But in C overflows on signed types absolutely are not Ok. > >> > > > > I disagree, overflows in DSP are normal. > > > > In some codecs like VP9 they're normative IIRC. > The C standard says they're undefined operations, and what the implementation > decides to do is something we don't care about as the input is invalid anyway > and we > can't salvage it.
ISO/IEC 9899:2017 3.4.3 1 undefined behavior behavior, upon use of a nonportable or erroneous program construct or of erroneous data, for which this International Standard imposes no requirements 2 Note 1 to entry: Possible undefined behavior ranges from ignoring the situation completely with unpredictable results, to behaving during translation or program execution in a documented manner characteristic of the environment (with or without the issuance of a diagnostic message), to terminating a translation or execution (with the issuance of a diagnostic message). 3 EXAMPLE An example of undefined behavior is the behavior on integer overflow. [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB I have often repented speaking, but never of holding my tongue. -- Xenocrates
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