Prevent loading byref-like types with invalid layout (#7584)

Port of dotnet/coreclr#25200.
dotnet · Jul 3, 2019 · d6f1d52 · d6f1d52
1 parent 050ad73
commit d6f1d52
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Showing 3 changed files with 37 additions and 3 deletions.
diff --git a/src/Common/src/TypeSystem/Common/MetadataFieldLayoutAlgorithm.cs b/src/Common/src/TypeSystem/Common/MetadataFieldLayoutAlgorithm.cs
@@ -315,7 +315,8 @@ private static ComputedInstanceFieldLayout ComputeExplicitFieldLayout(MetadataTy
 
             foreach (var fieldAndOffset in layoutMetadata.Offsets)
             {
-                var fieldSizeAndAlignment = ComputeFieldSizeAndAlignment(fieldAndOffset.Field.FieldType, packingSize);
+                TypeDesc fieldType = fieldAndOffset.Field.FieldType;
+                var fieldSizeAndAlignment = ComputeFieldSizeAndAlignment(fieldType, packingSize);
 
                 largestAlignmentRequired = LayoutInt.Max(fieldSizeAndAlignment.Alignment, largestAlignmentRequired);
 
@@ -324,12 +325,13 @@ private static ComputedInstanceFieldLayout ComputeExplicitFieldLayout(MetadataTy
 
                 LayoutInt computedOffset = fieldAndOffset.Offset + cumulativeInstanceFieldPos;
 
-                if (fieldAndOffset.Field.FieldType.IsGCPointer && !computedOffset.IsIndeterminate)
+                // GC pointers MUST be aligned.
+                // We treat byref-like structs as GC pointers too.
+                if (!computedOffset.IsIndeterminate && (fieldType.IsGCPointer || fieldType.IsByRefLike))
                 {
                     int offsetModulo = computedOffset.AsInt % type.Context.Target.PointerSize;
                     if (offsetModulo != 0)
                     {
-                        // GC pointers MUST be aligned.
                         ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadExplicitLayout, type, fieldAndOffset.Offset.ToStringInvariant());
                     }
                 }

diff --git a/src/ILCompiler.TypeSystem/tests/CoreTestAssembly/InstanceFieldLayout.cs b/src/ILCompiler.TypeSystem/tests/CoreTestAssembly/InstanceFieldLayout.cs
@@ -96,6 +96,24 @@ public class ExplicitEmptyClass
     public struct ExplicitEmptyStruct
     {
     }
+
+    [StructLayout(LayoutKind.Explicit)]
+    ref struct MisalignedPointer
+    {
+        [FieldOffset(2)]
+        public object O;
+    }
+
+    [StructLayout(LayoutKind.Explicit)]
+    ref struct MisalignedByRef
+    {
+        [FieldOffset(2)]
+        public ByRefStruct O;
+    }
+
+    ref struct ByRefStruct
+    {
+    }
 }
 
 namespace Sequential

diff --git a/src/ILCompiler.TypeSystem/tests/InstanceFieldLayoutTests.cs b/src/ILCompiler.TypeSystem/tests/InstanceFieldLayoutTests.cs
@@ -112,6 +112,20 @@ public void TestExplicitTypeLayoutWithInheritance()
             }
         }
 
+        [Fact]
+        public void TestInvalidExplicitTypeLayout()
+        {
+            {
+                DefType type = _testModule.GetType("Explicit", "MisalignedPointer");
+                Assert.Throws<TypeSystemException.TypeLoadException>(() => type.ComputeInstanceLayout(InstanceLayoutKind.TypeAndFields));
+            }
+
+            {
+                DefType type = _testModule.GetType("Explicit", "MisalignedByRef");
+                Assert.Throws<TypeSystemException.TypeLoadException>(() => type.ComputeInstanceLayout(InstanceLayoutKind.TypeAndFields));
+            }
+        }
+
         [Fact]
         public void TestSequentialTypeLayout()
         {