[FFmpeg-devel] [PATCH] libavcodec/png_parser.c: fix a use_of_uninitialized_value in target_dec_fuzzer.

[Thierry Foucu]

On Thu, Jun 4, 2020 at 11:52 AM James Almer <jamrial at gmail.com> wrote:

> On 6/4/2020 3:40 PM, Thierry Foucu wrote:
> > target_dec_fuzzer is checking for the avpkt.data pointer but if the
> > png parser cannot combine the frame, the poutbuf is not set and so, the
> > avpkt.data is not initialized.
> > ---
> >  libavcodec/png_parser.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavcodec/png_parser.c b/libavcodec/png_parser.c
> > index 74f2964118..d1b2926154 100644
> > --- a/libavcodec/png_parser.c
> > +++ b/libavcodec/png_parser.c
> > @@ -99,8 +99,11 @@ static int png_parse(AVCodecParserContext *s,
> AVCodecContext *avctx,
> >      }
> >
> >  flush:
> > -    if (ff_combine_frame(&ppc->pc, next, &buf, &buf_size) < 0)
> > +    if (ff_combine_frame(&ppc->pc, next, &buf, &buf_size) < 0) {
> > +        *poutbuf = NULL;
> > +        *poutbuf_size = 0;
>
> This is already set to 0 first thing in png_parse(), so i'd say we
> should also set *poutbuf to NULL there instead.
>
> Good catch.. I will modify the patch.


> And I see the BMP parser has the same issue, so it needs the same fix.
>
> I will send a patch for BMP and also for MLP. Both have the same problem.


> >          return buf_size;
> > +    }
> >
> >      ppc->chunk_pos = ppc->pc.frame_start_found = 0;
> >
> >
>
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-- 

Thierry Foucu