[FFmpeg-cvslog] avcodec/diracdec: Prevent integer overflow in intermediate in global_mv()

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Sun Jul 22 18:58:34 2018 +0200| [00c3f178a8e52c353091013e09378cd37b3e4aa1] | committer: Michael Niedermayer

avcodec/diracdec: Prevent integer overflow in intermediate in global_mv()

Fixes: signed integer overflow: -393471 * 5460 cannot be represented in type 'int'
Fixes: 8890/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DIRAC_fuzzer-6299775379963904

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 51290406461ed40b70e0e05b389a461a283f3367)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=00c3f178a8e52c353091013e09378cd37b3e4aa1
---

 libavcodec/diracdec.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/diracdec.c b/libavcodec/diracdec.c
index 9801eb2c85..c345acfc85 100644
--- a/libavcodec/diracdec.c
+++ b/libavcodec/diracdec.c
@@ -1186,8 +1186,8 @@ static void global_mv(DiracContext *s, DiracBlock *block, int x, int y, int ref)
     int *c      = s->globalmc[ref].perspective;
 
     int m       = (1<<ep) - (c[0]*x + c[1]*y);
-    int64_t mx  = m * (int64_t)((A[0][0] * x + A[0][1]*y) + (1<<ez) * b[0]);
-    int64_t my  = m * (int64_t)((A[1][0] * x + A[1][1]*y) + (1<<ez) * b[1]);
+    int64_t mx  = m * (int64_t)((A[0][0] * (int64_t)x + A[0][1]*(int64_t)y) + (1<<ez) * b[0]);
+    int64_t my  = m * (int64_t)((A[1][0] * (int64_t)x + A[1][1]*(int64_t)y) + (1<<ez) * b[1]);
 
     block->u.mv[ref][0] = (mx + (1<<(ez+ep))) >> (ez+ep);
     block->u.mv[ref][1] = (my + (1<<(ez+ep))) >> (ez+ep);