[FFmpeg-cvslog] error concealment: initialize block index.

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michaelni at gmx.at> | Tue Jan 24 20:54:27 2012 +0100| [c77be3a35a0160d6af88056b0899f120f2eef38e] | committer: Michael Niedermayer

error concealment: initialize block index.

Fixes CVE-2011-3941 (out of bounds write)

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=c77be3a35a0160d6af88056b0899f120f2eef38e
---

 libavcodec/error_resilience.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/libavcodec/error_resilience.c b/libavcodec/error_resilience.c
index 8bb5d0c..d55c000 100644
--- a/libavcodec/error_resilience.c
+++ b/libavcodec/error_resilience.c
@@ -46,6 +46,9 @@ static void decode_mb(MpegEncContext *s, int ref)
     s->dest[1] = s->current_picture.f.data[1] + (s->mb_y * (16 >> s->chroma_y_shift) * s->uvlinesize) + s->mb_x * (16 >> s->chroma_x_shift);
     s->dest[2] = s->current_picture.f.data[2] + (s->mb_y * (16 >> s->chroma_y_shift) * s->uvlinesize) + s->mb_x * (16 >> s->chroma_x_shift);
 
+    ff_init_block_index(s);
+    ff_update_block_index(s);
+
     if (CONFIG_H264_DECODER && s->codec_id == CODEC_ID_H264) {
         H264Context *h = (void*)s;
         h->mb_xy = s->mb_x + s->mb_y * s->mb_stride;