From c4762cdfd5190de091d2a8b4624181a677af448e Mon Sep 17 00:00:00 2001
From: Stephen Halter <halter73@gmail.com>
Date: Tue, 17 Jan 2017 12:32:53 -0800
Subject: [PATCH] Better handle OnHeartbeat in 32-bit environments

- Prevent potential overflow when casting a long to an IntPtr
---
 .../Internal/Infrastructure/KestrelThread.cs  | 20 ++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/Microsoft.AspNetCore.Server.Kestrel/Internal/Infrastructure/KestrelThread.cs b/src/Microsoft.AspNetCore.Server.Kestrel/Internal/Infrastructure/KestrelThread.cs
index 87e48f5205..117efc08fc 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel/Internal/Infrastructure/KestrelThread.cs
+++ b/src/Microsoft.AspNetCore.Server.Kestrel/Internal/Infrastructure/KestrelThread.cs
@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Runtime.ExceptionServices;
+using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
@@ -25,8 +26,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
         private static readonly Action<object, object> _postAsyncCallbackAdapter = (callback, state) => ((Action<object>)callback).Invoke(state);
         private static readonly Libuv.uv_walk_cb _heartbeatWalkCallback = (ptr, arg) =>
         {
-            var handle = UvMemory.FromIntPtr<UvHandle>(ptr);
-            (handle as UvStreamHandle)?.Connection?.Tick((long)arg);
+            var streamHandle = UvMemory.FromIntPtr<UvHandle>(ptr) as UvStreamHandle;
+            var thisHandle = GCHandle.FromIntPtr(arg);
+            var kestrelThread = (KestrelThread)thisHandle.Target;
+            streamHandle?.Connection?.Tick(kestrelThread.Now);
         };
 
         // maximum times the work queues swapped and are processed in a single pass
@@ -53,6 +56,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
         private readonly IKestrelTrace _log;
         private readonly IThreadPool _threadPool;
         private readonly TimeSpan _shutdownTimeout;
+        private IntPtr _thisPtr;
 
         public KestrelThread(KestrelEngine engine)
         {
@@ -99,6 +103,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
 
         private Action<Action<IntPtr>, IntPtr> QueueCloseAsyncHandle { get; }
 
+        // The cached result of Loop.Now() which is a timestamp in milliseconds
+        private long Now { get; set; }
+
         public Task StartAsync()
         {
             var tcs = new TaskCompletionSource<int>();
@@ -303,8 +310,13 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
                 }
             }
 
+            // This is used to access a 64-bit timestamp (this.Now) using a potentially 32-bit IntPtr.
+            var thisHandle = GCHandle.Alloc(this, GCHandleType.Weak);
+
             try
             {
+                _thisPtr = GCHandle.ToIntPtr(thisHandle);
+
                 _loop.Run();
                 if (_stopImmediate)
                 {
@@ -331,6 +343,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
             }
             finally
             {
+                thisHandle.Free();
                 _threadTcs.SetResult(null);
             }
         }
@@ -349,7 +362,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
 
         private void OnHeartbeat(UvTimerHandle timer)
         {
-            Walk(_heartbeatWalkCallback, (IntPtr)Loop.Now());
+            Now = Loop.Now();
+            Walk(_heartbeatWalkCallback, _thisPtr);
         }
 
         private bool DoPostWork()