Re: [FFmpeg-devel] [PATCH 3/3] avcodec/cbs_h2645: Avoid an unchecked bytesteram read

[Michael Niedermayer <michael@niedermayer.cc>]

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On Mon, Jul 24, 2023 at 11:28:20PM -0300, James Almer wrote:
> On 7/24/2023 9:46 PM, Michael Niedermayer wrote:
> > The unchecked read caused the 2nd subsequent tell call to move backward resulting
> > in a negative length
> > 
> > Fixes: assertion failure
> > Fixes: 60276/clusterfuzz-testcase-minimized-ffmpeg_BSF_TRACE_HEADERS_fuzzer-5434126636023808
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >   libavcodec/cbs_h2645.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
> > index 34c5d1d372..21c8bc76d5 100644
> > --- a/libavcodec/cbs_h2645.c
> > +++ b/libavcodec/cbs_h2645.c
> > @@ -695,7 +695,7 @@ static int cbs_h2645_split_fragment(CodedBitstreamContext *ctx,
> >               int nal_unit_type = bytestream2_get_byte(&gbc) & 0x1f;
> >               unsigned int num_nalus = 1;
> >               if(nal_unit_type != VVC_DCI_NUT && nal_unit_type != VVC_OPI_NUT)
> > -                num_nalus = bytestream2_get_be16u(&gbc);
> > +                num_nalus = bytestream2_get_be16(&gbc);
> >               start = bytestream2_tell(&gbc);
> >               for(i = 0; i < num_nalus; i++) {
> 
> LGTM.

will apply

thx

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