On Fri, May 05, 2023 at 07:36:05PM -0300, James Almer wrote: > On 4/16/2023 1:48 PM, Michael Niedermayer wrote: > > Fixes: signed integer overflow: 3011809745540902265 + 6323452730883571725 > > cannot be represented in type 'long' > > Fixes: > > 45982/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FLAC_fuzzer-6687553022722048 > > > > Found-by: continuous fuzzing process > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > --- > > libavcodec/flacdec.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/libavcodec/flacdec.c b/libavcodec/flacdec.c > > index cc778a8dff1..524a0469495 100644 > > --- a/libavcodec/flacdec.c > > +++ b/libavcodec/flacdec.c > > @@ -513,7 +513,7 @@ static int decode_subframe_lpc_33bps(FLACContext *s, > > int64_t *decoded, > > for (i = pred_order; i < s->blocksize; i++, decoded++) { > > int64_t sum = 0; > > for (j = 0; j < pred_order; j++) > > - sum += (int64_t)coeffs[j] * decoded[j]; > > + sum += (int64_t)coeffs[j] * (uint64_t)decoded[j]; > > Why not instead do > > sum = av_sat_add64(sum, (int64_t)coeffs[j] * decoded[j]);
Why should this be clipping ? flac is a lossless codec, i see nothing in the specification that calls for cliping. > > Also, decoded[j] is an int64_t, so wouldn't coeffs[j] be promoted if you > swap the order in the multiplication, thus saving the cast? it can be shuffled around to achieve the same, do you prefer coeffs[j] * (uint64_t)decoded[j]; ? thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Any man who breaks a law that conscience tells him is unjust and willingly accepts the penalty by staying in jail in order to arouse the conscience of the community on the injustice of the law is at that moment expressing the very highest respect for law. - Martin Luther King Jr
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