[FFmpeg-cvslog] avcodec/ralf: Fix integer overflow in decode_block()

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sun May 10 20:15:11 2020 +0200| [0c4330847c104fcf3ef929c1acee33b5b34c20db] | committer: Michael Niedermayer

avcodec/ralf: Fix integer overflow in decode_block()

Fixes: signed integer overflow: 289082077 - -2003141111 cannot be represented in type 'int'
Fixes: 20492/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_RALF_fuzzer-5196077752123392

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=0c4330847c104fcf3ef929c1acee33b5b34c20db
---

 libavcodec/ralf.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/libavcodec/ralf.c b/libavcodec/ralf.c
index 831728177e..08e8043e30 100644
--- a/libavcodec/ralf.c
+++ b/libavcodec/ralf.c
@@ -344,7 +344,8 @@ static int decode_block(AVCodecContext *avctx, GetBitContext *gb,
     int len, ch, ret;
     int dmode, mode[2], bits[2];
     int *ch0, *ch1;
-    int i, t, t2;
+    int i;
+    unsigned int t, t2;
 
     len = 12 - get_unary(gb, 0, 6);
 
@@ -409,8 +410,8 @@ static int decode_block(AVCodecContext *avctx, GetBitContext *gb,
         for (i = 0; i < len; i++) {
             t  =   ch1[i] + ctx->bias[1];
             t2 = ((ch0[i] + ctx->bias[0]) * 2) | (t & 1);
-            dst0[i] = (t2 + t) / 2;
-            dst1[i] = (t2 - t) / 2;
+            dst0[i] = (int)(t2 + t) / 2;
+            dst1[i] = (int)(t2 - t) / 2;
         }
         break;
     }