From 3ef00eaa0626489324fcd8c40466674058097605 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=97=B6=E6=97=A0=E4=B8=A4=E4=B8=B6?= <442367943@qq.com>
Date: Fri, 27 Sep 2019 03:53:35 +0800
Subject: [PATCH] Double check `size` to avoid `ArrayIndexOutOfBoundsException`
 (#9609)

Motivation:

Recycler$Stack.pop will occurs `ArrayIndexOutOfBoundsException` in some race cases, we should double check `size` even after `scavenge` called.

Modifications:

Double check `size` after `scavenge`

Result:

avoid ArrayIndexOutOfBoundsException in `pop`
---
 common/src/main/java/io/netty/util/Recycler.java | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/common/src/main/java/io/netty/util/Recycler.java b/common/src/main/java/io/netty/util/Recycler.java
index 9412424868..814d8e2109 100644
--- a/common/src/main/java/io/netty/util/Recycler.java
+++ b/common/src/main/java/io/netty/util/Recycler.java
@@ -511,6 +511,10 @@ public abstract class Recycler<T> {
                     return null;
                 }
                 size = this.size;
+                if (size <= 0) {
+                    // double check, avoid races
+                    return null;
+                }
             }
             size --;
             DefaultHandle ret = elements[size];