[FFmpeg-cvslog] avcodec/h264idct_template: Fix integer overflows in ff_h264_idct8_add()

[Michael Niedermayer]

ffmpeg | branch: release/3.4 | Michael Niedermayer <michael at niedermayer.cc> | Mon Oct 30 23:21:41 2017 +0100| [66e65e0a686a875fc4693e332bba6a2a221fe946] | committer: Michael Niedermayer

avcodec/h264idct_template: Fix integer overflows in ff_h264_idct8_add()

Fixes: runtime error: signed integer overflow: 924846844 + 1457520640 cannot be represented in type 'int'
Fixes: 3416/clusterfuzz-testcase-minimized-6125587682820096

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 2b739e1cb8f6ce8baead03ce5c999103ba78f24f)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=66e65e0a686a875fc4693e332bba6a2a221fe946
---

 libavcodec/h264idct_template.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libavcodec/h264idct_template.c b/libavcodec/h264idct_template.c
index 3ad58c4a11..fbd07cb8d5 100644
--- a/libavcodec/h264idct_template.c
+++ b/libavcodec/h264idct_template.c
@@ -107,10 +107,10 @@ void FUNCC(ff_h264_idct8_add)(uint8_t *_dst, int16_t *_block, int stride){
     }
     for( i = 0; i < 8; i++ )
     {
-        const unsigned a0 =  block[0+i*8] + block[4+i*8];
-        const unsigned a2 =  block[0+i*8] - block[4+i*8];
-        const unsigned a4 = (block[2+i*8]>>1) - block[6+i*8];
-        const unsigned a6 = (block[6+i*8]>>1) + block[2+i*8];
+        const unsigned a0 =  block[0+i*8] + (unsigned)block[4+i*8];
+        const unsigned a2 =  block[0+i*8] - (unsigned)block[4+i*8];
+        const unsigned a4 = (block[2+i*8]>>1) - (unsigned)block[6+i*8];
+        const unsigned a6 = (block[6+i*8]>>1) + (unsigned)block[2+i*8];
 
         const unsigned b0 = a0 + a6;
         const unsigned b2 = a2 + a4;