[FFmpeg-cvslog] avcodec/snowdec: Fix ref value check

[Michael Niedermayer]

ffmpeg | branch: release/2.4 | Michael Niedermayer <michaelni at gmx.at> | Tue Feb 24 03:12:22 2015 +0100| [49543062280ccf2e961b01784d8bbbcf09e1197c] | committer: Michael Niedermayer

avcodec/snowdec: Fix ref value check

Fixes integer overflow and out of array read.
Fixes: signal_sigsegv_24169e6_3445_cov_3778346427_snow_chroma_bug.avi

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
(cherry picked from commit 8f4cbf940212079a34753c7f4d6c6b5a43586d30)

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=49543062280ccf2e961b01784d8bbbcf09e1197c
---

 libavcodec/snowdec.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/snowdec.c b/libavcodec/snowdec.c
index 327157b..c5fa203 100644
--- a/libavcodec/snowdec.c
+++ b/libavcodec/snowdec.c
@@ -152,7 +152,7 @@ static int decode_q_branch(SnowContext *s, int level, int x, int y){
         int l = left->color[0];
         int cb= left->color[1];
         int cr= left->color[2];
-        int ref = 0;
+        unsigned ref = 0;
         int ref_context= av_log2(2*left->ref) + av_log2(2*top->ref);
         int mx_context= av_log2(2*FFABS(left->mx - top->mx)) + 0*av_log2(2*FFABS(tr->mx - top->mx));
         int my_context= av_log2(2*FFABS(left->my - top->my)) + 0*av_log2(2*FFABS(tr->my - top->my));