[SPARK-23391][CORE] It may lead to overflow for some integer multipli…

…cation

In the `getBlockData`,`blockId.reduceId` is the `Int` type, when it is greater than 2^28, `blockId.reduceId*8` will overflow
In the `decompress0`, `len` and  `unitSize` are  Int type, so `len * unitSize` may lead to  overflow
N/A

Author: liuxian <[email protected]>

Closes #20581 from 10110346/overflow2.

(cherry picked from commit 4a4dd4f)
Signed-off-by: Sean Owen <[email protected]>

core/src/main/scala/org/apache/spark/shuffle/IndexShuffleBlockResolver.scala

@@ -203,13 +203,13 @@ private[spark] class IndexShuffleBlockResolver(
     // class of issue from re-occurring in the future which is why they are left here even though
     // SPARK-22982 is fixed.
     val channel = Files.newByteChannel(indexFile.toPath)
-    channel.position(blockId.reduceId * 8)
+    channel.position(blockId.reduceId * 8L)
     val in = new DataInputStream(Channels.newInputStream(channel))
     try {
       val offset = in.readLong()
       val nextOffset = in.readLong()
       val actualPosition = channel.position()
-      val expectedPosition = blockId.reduceId * 8 + 16
+      val expectedPosition = blockId.reduceId * 8L + 16
       if (actualPosition != expectedPosition) {
         throw new Exception(s"SPARK-22982: Incorrect channel position after index file reads: " +
           s"expected $expectedPosition but actual position was $actualPosition.")