[ILVerify] Fixed range checks for nested exception regions (#4056)

2 files changed, 50 insertions, 4 deletions

diff --git a/src/ILVerify/src/ILImporter.Verify.cs b/src/ILVerify/src/ILImporter.Verify.cs
index fc732a8a2..30cf77cca 100644
--- a/src/ILVerify/src/ILImporter.Verify.cs
+++ b/src/ILVerify/src/ILImporter.Verify.cs
@@ -170,8 +170,8 @@ namespace Internal.IL
                 for (int j = 0; j < _exceptionRegions.Length; j++)
                 {
                     var r = _exceptionRegions[j].ILRegion;
-
-                    if (r.TryOffset <= offset && r.TryOffset + r.TryLength >= offset)
+                    // Check if offset is within the range [TryOffset, TryOffset + TryLength[
+                    if (r.TryOffset <= offset && offset < r.TryOffset + r.TryLength)
                     {
                         if (!basicBlock.TryIndex.HasValue)
                         {
@@ -189,7 +189,8 @@ namespace Internal.IL
                             }
                         }
                     }
-                    if (r.HandlerOffset <= offset && r.HandlerOffset + r.HandlerLength >= offset)
+                    // Check if offset is within the range [HandlerOffset, HandlerOffset + HandlerLength[
+                    if (r.HandlerOffset <= offset && offset < r.HandlerOffset + r.HandlerLength)
                     {
                         if (!basicBlock.HandlerIndex.HasValue)
                         {
@@ -207,7 +208,8 @@ namespace Internal.IL
                             }
                         }
                     }
-                    if(r.FilterOffset != -1 && r.FilterOffset <= offset && r.HandlerOffset - 1 >= offset)
+                    // Check if offset is within the range [FilterOffset, HandlerOffset[
+                    if (r.FilterOffset != -1 && r.FilterOffset <= offset && offset < r.HandlerOffset )
                     {
                         if(!basicBlock.FilterIndex.HasValue)
                         {
@@ -547,6 +549,8 @@ namespace Internal.IL
 
             if (basicBlock.EntryStack?.Length > 0)
             {
+                if (_stack == null || _stack.Length < basicBlock.EntryStack.Length)
+                    Array.Resize(ref _stack, basicBlock.EntryStack.Length);
                 Array.Copy(basicBlock.EntryStack, _stack, basicBlock.EntryStack.Length);
                 _stackTop = basicBlock.EntryStack.Length;
             }
diff --git a/src/ILVerify/tests/ILTests/ExceptionRegionTests.il b/src/ILVerify/tests/ILTests/ExceptionRegionTests.il
new file mode 100644
index 000000000..840643c39
--- /dev/null
+++ b/src/ILVerify/tests/ILTests/ExceptionRegionTests.il
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+.assembly extern System.Runtime
+{
+}
+
+.assembly ExceptionRegion
+{
+}
+
+.class public sequential ansi sealed beforefieldinit ExceptionRegionTests
+       extends [System.Runtime]System.Object
+{
+    .method public instance void ExceptionRegion.NestedTryFinally_Valid() cil managed
+    {
+        .try  
+        { 
+            nop
+            leave EndTryCatch
+        } 
+        finally
+        {
+            .try 
+            { 
+                nop
+                leave EndFinally
+            } 
+            catch [System.Runtime]System.Exception
+            {
+                nop
+                leave EndFinally
+            }
+EndFinally:
+            endfinally
+        }
+EndTryCatch:
+        ret
+    }
+}
+