[FFmpeg-devel] [PATCH] iff: do not decode unsupported pbms with ham decoder

[Peter Ross]

On Sun, Mar 11, 2012 at 11:48:11PM +0000, Paul B Mahol wrote:
> On 3/11/12, Peter Ross <pross at xvid.org> wrote:
> > This prevents the segfault reported by ticket #1054
> 
> Does this fix real source of crash or just adds "workaround"?

Yes, it fixes the source of the segfault.

The 's->ham_buf' buffer is only allocated for HAM images, yet
we were invoking the HAM decoder anyway for unsupported non-HAM
images. Writing to the allocated buffer triggered the segfault.

So this patch places a 'if (s->ham) {' guard around the decoder,
and print out an appropriate warning for unsupported files.

> >
> > ---
> >  libavcodec/iff.c |    5 ++++-
> >  1 files changed, 4 insertions(+), 1 deletions(-)
> >
> > diff --git a/libavcodec/iff.c b/libavcodec/iff.c
> > index 9b09604..30ce70d 100644
> > --- a/libavcodec/iff.c
> > +++ b/libavcodec/iff.c
> > @@ -635,12 +635,15 @@ static int decode_frame_byterun1(AVCodecContext
> > *avctx,
> >              uint8_t *row = &s->frame.data[0][y*s->frame.linesize[0]];
> >              buf += decode_byterun(row, avctx->width, buf, buf_end);
> >          }
> > -    } else { // IFF-PBM: HAM to PIX_FMT_BGR32
> > +    } else if (s->ham) { // IFF-PBM: HAM to PIX_FMT_BGR32
> >          for (y = 0; y < avctx->height ; y++) {
> >              uint8_t *row = &s->frame.data[0][y*s->frame.linesize[0]];
> >              buf += decode_byterun(s->ham_buf, avctx->width, buf, buf_end);
> >              decode_ham_plane32((uint32_t *) row, s->ham_buf, s->ham_palbuf,
> > s->planesize);
> >          }
> > +    } else {
> > +        av_log_ask_for_sample(avctx, "unsupported bpp\n");
> OK, alternatively it could be treated as invalid.
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-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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