Fix #1234: handle exception when a field initial value is not available

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -1199,8 +1199,13 @@ namespace ICSharpCode.Decompiler.CSharp
 				// Field data as specified in II.16.3.2 of ECMA-335 6th edition:
 				// .data I_X = int32(123)
 				// .field public static int32 _x at I_X
-				var initVal = fieldDefinition.GetInitialValue(module.PEFile.Reader, TypeSystem);
-				var message = string.Format(" Not supported: data({0}) ", BitConverter.ToString(initVal.ReadBytes(initVal.RemainingBytes)).Replace('-', ' '));
+				string message;
+				try {
+					var initVal = fieldDefinition.GetInitialValue(module.PEFile.Reader, TypeSystem);
+					message = string.Format(" Not supported: data({0}) ", BitConverter.ToString(initVal.ReadBytes(initVal.RemainingBytes)).Replace('-', ' '));
+				} catch (BadImageFormatException ex) {
+					message = ex.Message;
+				}
 				((FieldDeclaration)fieldDecl).Variables.Single().AddChild(new Comment(message, CommentType.MultiLine), Roles.Comment);
 			}
 			return fieldDecl;

ICSharpCode.Decompiler/Metadata/Dom.cs

@@ -92,6 +92,8 @@ namespace ICSharpCode.Decompiler.Metadata
 			var reader = sectionData.GetReader();
 			reader.Offset += (int)This().Offset;
 			int length = reader.ReadInt32();
+			if (length < 0 || length > reader.RemainingBytes)
+				throw new BadImageFormatException("Resource stream length invalid");
 			return new ResourceMemoryStream(Module.Reader, reader.CurrentPointer, length);
 		}
 	}

ICSharpCode.Decompiler/SRMExtensions.cs

@@ -337,11 +337,18 @@ namespace ICSharpCode.Decompiler
 
 		public static unsafe SRM.BlobReader GetInitialValue(this FieldDefinition field, PEReader pefile, ICompilation typeSystem)
 		{
-			if (!field.HasFlag(FieldAttributes.HasFieldRVA) || field.GetRelativeVirtualAddress() == 0)
+			if (!field.HasFlag(FieldAttributes.HasFieldRVA))
 				return default;
 			int rva = field.GetRelativeVirtualAddress();
+			if (rva == 0)
+				return default;
 			int size = field.DecodeSignature(new FieldValueSizeDecoder(typeSystem), default);
-			return pefile.GetSectionData(rva).GetReader(0, size);
+			var sectionData = pefile.GetSectionData(rva);
+			if (sectionData.Length == 0 && size != 0)
+				throw new BadImageFormatException($"Field data (rva=0x{rva:x}) could not be found in any section!");
+			if (size < 0 || size > sectionData.Length)
+				throw new BadImageFormatException($"Invalid size {size} for field data!");
+			return sectionData.GetReader(0, size);
 		}
 
 		sealed class FieldValueSizeDecoder : ISignatureTypeProvider<int, GenericContext>