avcodec/truemotion2: Fix several integer overflows in tm2_motion_block()

Fixes: 15524/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TRUEMOTION2_fuzzer-5173148372172800
Fixes: signed integer overflow: 13701388 - -2134868270 cannot be represented in type 'int'
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/truemotion2.c b/libavcodec/truemotion2.c
index a86dd16e0fef6c1c3b0861e7fcb59241786b4271..5d6dfc24c395faae71aabe9ff795bf25446c8610 100644 (file)
--- a/libavcodec/truemotion2.c
+++ b/libavcodec/truemotion2.c
@@ -764,10 +764,10 @@ static inline void tm2_motion_block(TM2Context *ctx, AVFrame *pic, int bx, int b
     }
     /* calculate deltas */
     Y -= Ystride * 4;
-    ctx->D[0] = Y[3] - last[3];
-    ctx->D[1] = Y[3 + Ystride] - Y[3];
-    ctx->D[2] = Y[3 + Ystride * 2] - Y[3 + Ystride];
-    ctx->D[3] = Y[3 + Ystride * 3] - Y[3 + Ystride * 2];
+    ctx->D[0] = (unsigned)Y[3] - last[3];
+    ctx->D[1] = (unsigned)Y[3 + Ystride] - Y[3];
+    ctx->D[2] = (unsigned)Y[3 + Ystride * 2] - Y[3 + Ystride];
+    ctx->D[3] = (unsigned)Y[3 + Ystride * 3] - Y[3 + Ystride * 2];
     for (i = 0; i < 4; i++)
         last[i] = Y[i + Ystride * 3];
 }