On Wed, Jun 19, 2024 at 03:08:58PM +0200, Rémi Denis-Courmont wrote: > > > Le 19 juin 2024 14:34:59 GMT+02:00, James Almer <jamr...@gmail.com> a écrit : > >On 6/18/2024 4:07 AM, Rémi Denis-Courmont wrote: > >> > >> > >> Le 17 juin 2024 01:08:27 GMT+02:00, Michael Niedermayer > >> <mich...@niedermayer.cc> a écrit : > >>> Fixes: signed integer overflow: 2314885530818453536 + 9151314442816847872 > >>> cannot be represented in type 'long' > >>> Fixes: > >>> 68359/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-6571950311800832 > >>> > >>> Found-by: continuous fuzzing process > >>> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > >>> Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > >>> --- > >>> libavformat/mov.c | 4 +++- > >>> 1 file changed, 3 insertions(+), 1 deletion(-) > >>> > >>> diff --git a/libavformat/mov.c b/libavformat/mov.c > >>> index 9016cd5ad08..46cbce98040 100644 > >>> --- a/libavformat/mov.c > >>> +++ b/libavformat/mov.c > >>> @@ -8131,7 +8131,9 @@ static int mov_read_iloc(MOVContext *c, AVIOContext > >>> *pb, MOVAtom atom) > >>> } > >>> for (int j = 0; j < extent_count; j++) { > >>> if (rb_size(pb, &extent_offset, offset_size) < 0 || > >>> - rb_size(pb, &extent_length, length_size) < 0) > >>> + rb_size(pb, &extent_length, length_size) < 0 || > >>> + base_offset < 0 || extent_offset < 0 || > >>> + base_offset + (uint64_t)extent_offset > INT64_MAX) > >> > >> Can we please stop with the bespoke arithmetic overflow checks and add > >> dedicated helpers instead, similar to what GCC and C23 have? > > > >You mean the __builtin_*_overflow() one? > > I'd rather the ckd_*() stuff but the differences are mostly stylistic.
Whatever is used must be supported by all currently supported platforms that especially also includes past releases we backport things to. In practice that means continuing to use the classical way to check as well as our av_sat_addXY() stuff. We cannot backport things that depend on C23 as that was not a requirement in the past. So I also cannot use this in bug fixes. thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB The smallest minority on earth is the individual. Those who deny individual rights cannot claim to be defenders of minorities. - Ayn Rand
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