8314236: Overflow in Collections.rotate

Co-authored-by: Nikita Sakharin <17588081+nikita-sakharin@users.noreply.github.com>
Reviewed-by: shade, smarks

src/java.base/share/classes/java/util/Collections.java

@@ -816,15 +816,16 @@ public class Collections {
         if (distance == 0)
             return;
 
-        for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) {
+        int bound = size - distance;
+        for (int cycleStart = 0, nMoved = 0; nMoved < size; cycleStart++) {
             T displaced = list.get(cycleStart);
             int i = cycleStart;
             do {
-                i += distance;
-                if (i >= size)
+                if (i >= bound)
                     i -= size;
+                i += distance;
                 displaced = list.set(i, displaced);
-                nMoved ++;
+                nMoved++;
             } while (i != cycleStart);
         }
     }

test/jdk/java/util/Collections/RotateHuge.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8314236
+ * @summary Overflow in Collections.rotate
+ */
+
+import java.util.AbstractList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+import java.util.RandomAccess;
+
+public class RotateHuge {
+
+    private static final class MockList extends AbstractList<Object>
+            implements RandomAccess {
+        private final int size;
+
+        public MockList(final int size) {
+            if (size < 0)
+                throw new IllegalArgumentException("Illegal size: " + size);
+            this.size = size;
+        }
+
+        @Override
+        public Object get(final int index) {
+            Objects.checkIndex(index, size);
+            return null;
+        }
+
+        @Override
+        public Object set(final int index, final Object element) {
+            Objects.checkIndex(index, size);
+            return null;
+        }
+
+        @Override
+        public int size() {
+            return size;
+        }
+    }
+
+    public static void main(final String[] args) {
+        testRotate((1 << 30) + 1, -(1 << 30) - 2);
+        testRotate((1 << 30) + 1, 1 << 30);
+        testRotate(Integer.MAX_VALUE, Integer.MIN_VALUE);
+        testRotate(Integer.MAX_VALUE, Integer.MIN_VALUE + 3);
+        testRotate(Integer.MAX_VALUE, 2);
+        testRotate(Integer.MAX_VALUE, Integer.MAX_VALUE - 1);
+    }
+
+    /*
+     * This test covers only index computations.
+     * Correctness of elements rotation is not checked.
+     */
+    private static void testRotate(final int size, final int distance) {
+        final List<Object> list = new MockList(size);
+        Collections.rotate(list, distance);
+    }
+}