Re: [FFmpeg-devel] [PATCH 3/5] avcodec/rv60dec: Check sum in read_slice_sizes()

[Michael Niedermayer <michael@niedermayer.cc>]

[-- Attachment #1.1: Type: text/plain, Size: 2131 bytes --]

Hi Peter

On Sun, Jun 22, 2025 at 02:38:46PM +1000, Peter Ross wrote:
> On Sat, Jun 21, 2025 at 11:15:19PM +0200, Michael Niedermayer wrote:
> > Fixes: signed integer overflow: 2147483647 + 1913651185 cannot be represented in type 'int'
> > Fixes: 418335931/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_RV60_fuzzer-6568264620900352
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >  libavcodec/rv60dec.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/libavcodec/rv60dec.c b/libavcodec/rv60dec.c
> > index 2bbcb1d6209..dbafa7eed02 100644
> > --- a/libavcodec/rv60dec.c
> > +++ b/libavcodec/rv60dec.c
> > @@ -409,6 +409,8 @@ static int read_slice_sizes(RV60Context *s, GetBitContext *gb)
> >          if (last_size <= 0)
> >              return AVERROR_INVALIDDATA;
> >          s->slice[i].size = last_size;
> > +        if (s->slice[i].size > INT32_MAX - sum)
> > +            return AVERROR_INVALIDDATA;
> >          sum += s->slice[i].size;
> 
> As it turns out, sum is not used for any purpose.
> This patch (https://lists.ffmpeg.org/pipermail/ffmpeg-devel/2025-June/345621.html)
> drops sum, obviating the need for your patch.
> 
> However later on in rv60dec.c, line ~2354, there is a similar summation
> of slice sizes. This might need a INT_MAX guard?
> 
>       for (int i = 0; i < s->cu_height; i++) {
>           if (header_size + ofs >= avpkt->size)
>               return AVERROR_INVALIDDATA;
>           s->slice[i].data = avpkt->data + header_size + ofs;
>           s->slice[i].data_size = FFMIN(s->slice[i].size, avpkt->size - header_size - ofs);
>           ofs += s->slice[i].size;
>       }

teh same testcase also triggers the overflow on the 2nd case if it
gets past the first

new patch posted

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 195 bytes --]

[-- Attachment #2: Type: text/plain, Size: 251 bytes --]

_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

To unsubscribe, visit link above, or email
ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".