On Sun, Oct 02, 2022 at 07:13:39PM +0300, Rémi Denis-Courmont wrote: > Le sunnuntaina 2. lokakuuta 2022, 18.43.23 EEST Michael Niedermayer a écrit : > > Fixes: signed integer overflow: 2040812214 + 255101526 cannot be represented > > in type 'int' Fixes: > > 51323/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_BONK_fuzzer-4791481 > > 067503616 > > > > Found-by: continuous fuzzing process > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > Signed-off-by: Michael Niedermayer <[email protected]> > > --- > > libavcodec/bonk.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/libavcodec/bonk.c b/libavcodec/bonk.c > > index 409694f710d..32f7c9b9bdb 100644 > > --- a/libavcodec/bonk.c > > +++ b/libavcodec/bonk.c > > @@ -187,6 +187,9 @@ static int intlist_read(BonkContext *s, int *buf, int > > entries, int base_2_part) if (!dominant) > > n_zeros += steplet; > > > > + if (step > INT_MAX/9*8)
if you want the exact limit for any INT_MAX its:
(INT_MAX + 1ULL) / 9 * 8 + (INT_MAX + 1ULL) % 9 - 1;
though probably a fixed bit value would be better anyway for reproducability
> > + return AVERROR_INVALIDDATA;
> > +
> > step += step / 8;
> > } else if (steplet > 0) {
> > int actual_run = read_uint_max(s, steplet - 1);
>
> No problem with this patch *specifically* but wouldn't it be more effective
> to
> fix that sort of issue with checked arithmetic, e.g. something like:
>
> if (av_ckd_add(&step, step, step / 8))
> return AVERROR_INVALIDDATA;
>
> ...especially on 64-bit systems whence this is really just an add. This also
> avoids having to figure out what the exact boundary value is.
If someone has a set of testfiles for this decoder then I can look at this
and cleanup the code more completely.
i dont know if a step > C vs overflow check is better but i have the suspicion
there are more problems as multiple statments around this seem unreachable.
And iam also missing some check that i would expect to be in there
I found links to datafilehost.com to test files but they are all expired
so i have no test files, so iam a bit cautious with changes ...
CCing piotr who linked to the files on datafilehost, maybe he still has
them.
thx
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
In fact, the RIAA has been known to suggest that students drop out
of college or go to community college in order to be able to afford
settlements. -- The RIAA
signature.asc
Description: PGP signature
_______________________________________________ ffmpeg-devel mailing list [email protected] https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
