avformat/matroskaenc: Fix and simplify check for invalid crop values

The check "left >= INT_MAX - right" is supposed to check for
whether left + right does not overflow/wraparound, but given that
left and top are uint32_t INT_MAX - right can already wraparound
for big values of right (and ordinary 32-bit ints):
If right == UINT32_MAX, INT_MAX - right is INT_MAX + 1;
for left in 0..par->width both checks will be passed.

Fix this and simplify the check by using 64-bit types,
where the addition is guaranteed not to overflow.

Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavformat/matroskaenc.c

@@ -1786,16 +1786,14 @@ static int mkv_write_track_video(AVFormatContext *s, MatroskaMuxContext *mkv,
                                  st->codecpar->nb_coded_side_data,
                                  AV_PKT_DATA_FRAME_CROPPING);
     if (sd && sd->size == sizeof(uint32_t) * 4) {
-        uint32_t top, bottom, left, right;
+        uint64_t top, bottom, left, right;
 
         top    = AV_RL32(sd->data +  0);
         bottom = AV_RL32(sd->data +  4);
         left   = AV_RL32(sd->data +  8);
         right  = AV_RL32(sd->data + 12);
 
-        if (left >= INT_MAX - right ||
-            top >= INT_MAX - bottom ||
-            (left + right) >= par->width ||
+        if ((left + right) >= par->width ||
             (top + bottom) >= par->height) {
             av_log(s, AV_LOG_ERROR, "Invalid cropping dimensions in stream side data\n");
             return AVERROR(EINVAL);