[FFmpeg-cvslog] mss2: only use error correction for matching block counts

[Andreas Cadhalpun]

ffmpeg | branch: release/3.1 | Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com> | Thu Nov 24 23:57:46 2016 +0100| [072246993acb9ce22f88e3df697f78dba61fcdd3] | committer: Andreas Cadhalpun

mss2: only use error correction for matching block counts

This fixes a heap-buffer-overflow in ff_er_frame_end when decoding mss2
with coded_width/coded_height larger than width/height.

Reviewed-by: Michael Niedermayer <michael at niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
(cherry picked from commit 2566ad98b01538ea589e5ee07b69fc566aadc348)
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=072246993acb9ce22f88e3df697f78dba61fcdd3
---

 libavcodec/mss2.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libavcodec/mss2.c b/libavcodec/mss2.c
index d255dd4..fdc0716 100644
--- a/libavcodec/mss2.c
+++ b/libavcodec/mss2.c
@@ -422,7 +422,13 @@ static int decode_wmv9(AVCodecContext *avctx, const uint8_t *buf, int buf_size,
 
     ff_vc1_decode_blocks(v);
 
-    ff_er_frame_end(&s->er);
+    if (v->end_mb_x == s->mb_width && s->end_mb_y == s->mb_height) {
+        ff_er_frame_end(&s->er);
+    } else {
+        av_log(v->s.avctx, AV_LOG_WARNING,
+               "disabling error correction due to block count mismatch %dx%d != %dx%d\n",
+               v->end_mb_x, s->end_mb_y, s->mb_width, s->mb_height);
+    }
 
     ff_mpv_frame_end(s);