[FFmpeg-cvslog] h264: check for invalid zeros_left before writing

[Ronald S. Bultje]

ffmpeg | branch: master | Ronald S. Bultje <rsbultje at gmail.com> | Fri Dec  7 13:09:20 2012 -0800| [ddd7559ad97d3cde401ce096262af6375685ea22] | committer: Luca Barbato

h264: check for invalid zeros_left before writing

Prevent an invalid write into coeffs[scantable[-1]] if zeros_left
itself was an invalid VLC code (and thus -1).

Signed-off-by: Luca Barbato <lu_zero at gentoo.org>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ddd7559ad97d3cde401ce096262af6375685ea22
---

 libavcodec/h264_cavlc.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/libavcodec/h264_cavlc.c b/libavcodec/h264_cavlc.c
index 8702122..0cc7214 100644
--- a/libavcodec/h264_cavlc.c
+++ b/libavcodec/h264_cavlc.c
@@ -610,17 +610,18 @@ static int decode_residual(H264Context *h, GetBitContext *gb, DCTELEM *block, in
         } \
     }
 
+    if (zeros_left < 0) {
+        av_log(h->s.avctx, AV_LOG_ERROR,
+               "negative number of zero coeffs at %d %d\n", s->mb_x, s->mb_y);
+        return AVERROR_INVALIDDATA;
+    }
+
     if (h->pixel_shift) {
         STORE_BLOCK(int32_t)
     } else {
         STORE_BLOCK(int16_t)
     }
 
-    if(zeros_left<0){
-        av_log(h->s.avctx, AV_LOG_ERROR, "negative number of zero coeffs at %d %d\n", s->mb_x, s->mb_y);
-        return -1;
-    }
-
     return 0;
 }