[FFmpeg-cvslog] vc1: mquant is not allowed to be 0

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michaelni at gmx.at> | Fri Mar  2 18:24:21 2012 +0100| [64c58f143604223fa02ad4f11b40fb128f72aae5] | committer: Michael Niedermayer

vc1: mquant is not allowed to be 0

Fixes out of bounds read.
Checked against SMPTE 421M-2006

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=64c58f143604223fa02ad4f11b40fb128f72aae5
---

 libavcodec/vc1dec.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index 2d3a94c..6fb6b17 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -1174,6 +1174,10 @@ static void vc1_mc_4mv_chroma4(VC1Context *v)
                     mquant = v->pq + mqdiff;                   \
                 else                                           \
                     mquant = get_bits(gb, 5);                  \
+                if (!mquant) {                                 \
+                    av_log(v->s.avctx,AV_LOG_ERROR, "zero mquant\n");   \
+                    mquant = 1;                                \
+                }                                              \
             }                                                  \
         }                                                      \
         if (v->dqprofile == DQPROFILE_SINGLE_EDGE)             \