diracdec: check that block length is valid

In init_planes p->xblen and p->yblen are set to:
            p->xblen = s->plane[0].xblen >> s->chroma_x_shift;
            p->yblen = s->plane[0].yblen >> s->chroma_y_shift;

These are later used as block_w and block_h arguments of
s->vdsp.emulated_edge_mc. If one of them is 0 it triggers an av_assert2
in emulated_edge_mc:
    av_assert2(start_x < end_x && block_w > 0);
    av_assert2(start_y < end_y && block_h > 0);

Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 8 insertions, 0 deletions

diff --git a/libavcodec/diracdec.c b/libavcodec/diracdec.c
index e60147a01e..dbf2fd1b84 100644
--- a/libavcodec/diracdec.c
+++ b/libavcodec/diracdec.c
@@ -902,6 +902,14 @@ static int dirac_unpack_prediction_parameters(DiracContext *s)
     /*[DIRAC_STD] 11.2.4 motion_data_dimensions()
       Calculated in function dirac_unpack_block_motion_data */
 
+    if (s->plane[0].xblen % (1 << s->chroma_x_shift) != 0 ||
+        s->plane[0].yblen % (1 << s->chroma_y_shift) != 0 ||
+        !s->plane[0].xblen || !s->plane[0].yblen) {
+        av_log(s->avctx, AV_LOG_ERROR,
+               "invalid x/y block length (%d/%d) for x/y chroma shift (%d/%d)\n",
+               s->plane[0].xblen, s->plane[0].yblen, s->chroma_x_shift, s->chroma_y_shift);
+        return AVERROR_INVALIDDATA;
+    }
     if (!s->plane[0].xbsep || !s->plane[0].ybsep || s->plane[0].xbsep < s->plane[0].xblen/2 || s->plane[0].ybsep < s->plane[0].yblen/2) {
         av_log(s->avctx, AV_LOG_ERROR, "Block separation too small\n");
         return AVERROR_INVALIDDATA;