[FFmpeg-cvslog] Prevent block size from inreasing in the shorten decoder.

[Laurent Aimar]

ffmpeg | branch: release/0.8 | Laurent Aimar <fenrir at elivagar.org> | Sat Oct  1 00:43:05 2011 +0200| [55a96a984ec65736475a8577a158abc5c48fd50a] | committer: Michael Niedermayer

Prevent block size from inreasing in the shorten decoder.

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
(cherry picked from commit b399cbfba5d901608c18e1a2d48a24c30541a634)

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=55a96a984ec65736475a8577a158abc5c48fd50a
---

 libavcodec/shorten.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/libavcodec/shorten.c b/libavcodec/shorten.c
index 5e599fd..4c1abe8 100644
--- a/libavcodec/shorten.c
+++ b/libavcodec/shorten.c
@@ -483,9 +483,15 @@ static int shorten_decode_frame(AVCodecContext *avctx,
             case FN_BITSHIFT:
                 s->bitshift = get_ur_golomb_shorten(&s->gb, BITSHIFTSIZE);
                 break;
-            case FN_BLOCKSIZE:
-                s->blocksize = get_uint(s, av_log2(s->blocksize));
+            case FN_BLOCKSIZE: {
+                int blocksize = get_uint(s, av_log2(s->blocksize));
+                if (blocksize > s->blocksize) {
+                    av_log(avctx, AV_LOG_ERROR, "Increasing block size is not supported\n");
+                    return AVERROR_PATCHWELCOME;
+                }
+                s->blocksize = blocksize;
                 break;
+            }
             case FN_QUIT:
                 *data_size = 0;
                 return buf_size;