Fix garbage data in GetColumnSchema. Fixes #354

Author: bgrainger

src/MySqlConnector/MySqlClient/Results/ResultSet.cs

@@ -24,6 +24,7 @@ public async Task<ResultSet> ReadResultSetHeaderAsync(IOBehavior ioBehavior)
 			LastInsertId = 0;
 			RecordsAffected = 0;
 			State = ResultSetState.None;
+			m_columnDefinitionPayloadUsedBytes = 0;
 			m_dataLengths = null;
 			m_dataOffsets = null;
 			m_readBuffer.Clear();
@@ -83,14 +84,25 @@ public async Task<ResultSet> ReadResultSetHeaderAsync(IOBehavior ioBehavior)
 						if (reader.BytesRemaining != 0)
 							throw new MySqlException("Unexpected data at end of column_count packet; see https://github.com/mysql-net/MySqlConnector/issues/324");
 
+						// reserve adequate space to hold a copy of all column definitions (but note that this can be resized below if we guess too small)
+						Array.Resize(ref m_columnDefinitionPayloads, columnCount * 96);
+
 						ColumnDefinitions = new ColumnDefinitionPayload[columnCount];
 						m_dataOffsets = new int[columnCount];
 						m_dataLengths = new int[columnCount];
 
 						for (var column = 0; column < ColumnDefinitions.Length; column++)
 						{
 							payload = await Session.ReceiveReplyAsync(ioBehavior, CancellationToken.None).ConfigureAwait(false);
-							ColumnDefinitions[column] = ColumnDefinitionPayload.Create(payload);
+							var arraySegment = payload.ArraySegment;
+
+							// 'Session.ReceiveReplyAsync' reuses a shared buffer; make a copy so that the column definitions can always be safely read at any future point
+							if (m_columnDefinitionPayloadUsedBytes + arraySegment.Count > m_columnDefinitionPayloads.Length)
+								Array.Resize(ref m_columnDefinitionPayloads, Math.Max(m_columnDefinitionPayloadUsedBytes + arraySegment.Count, m_columnDefinitionPayloadUsedBytes * 2));
+							Buffer.BlockCopy(arraySegment.Array, arraySegment.Offset, m_columnDefinitionPayloads, m_columnDefinitionPayloadUsedBytes, arraySegment.Count);
+
+							ColumnDefinitions[column] = ColumnDefinitionPayload.Create(new ArraySegment<byte>(m_columnDefinitionPayloads, m_columnDefinitionPayloadUsedBytes, arraySegment.Count));
+							m_columnDefinitionPayloadUsedBytes += arraySegment.Count;
 						}
 
 						if (!Session.SupportsDeprecateEof)
@@ -421,6 +433,8 @@ public Row GetCurrentRow()
 		public int RecordsAffected { get; private set; }
 		public ResultSetState State { get; private set; }
 
+		byte[] m_columnDefinitionPayloads;
+		int m_columnDefinitionPayloadUsedBytes;
 		int[] m_dataLengths;
 		int[] m_dataOffsets;
 		readonly Queue<Row> m_readBuffer = new Queue<Row>();

src/MySqlConnector/Serialization/ColumnDefinitionPayload.cs

@@ -75,9 +75,9 @@ public string PhysicalName
 
 		public byte Decimals { get; private set; }
 
-		public static ColumnDefinitionPayload Create(PayloadData payload)
+		public static ColumnDefinitionPayload Create(ArraySegment<byte> arraySegment)
 		{
-			var reader = new ByteArrayReader(payload.ArraySegment);
+			var reader = new ByteArrayReader(arraySegment);
 			SkipLengthEncodedByteString(ref reader); // catalog
 			SkipLengthEncodedByteString(ref reader); // schema
 			SkipLengthEncodedByteString(ref reader); // table
@@ -105,7 +105,7 @@ public static ColumnDefinitionPayload Create(PayloadData payload)
 
 			return new ColumnDefinitionPayload
 			{
-				OriginalPayload = payload,
+				OriginalData = arraySegment,
 				CharacterSet = characterSet,
 				ColumnLength = columnLength,
 				ColumnType = columnType,
@@ -122,7 +122,7 @@ private static void SkipLengthEncodedByteString(ref ByteArrayReader reader)
 
 		private void ReadNames()
 		{
-			var reader = new ByteArrayReader(OriginalPayload.ArraySegment);
+			var reader = new ByteArrayReader(OriginalData);
 			m_catalogName = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
 			m_schemaName = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
 			m_table = Encoding.UTF8.GetString(reader.ReadLengthEncodedByteString());
@@ -132,7 +132,7 @@ private void ReadNames()
 			m_readNames = true;
 		}
 
-		PayloadData OriginalPayload { get; set; }
+		ArraySegment<byte> OriginalData { get; set; }
 
 		bool m_readNames;
 		string m_name;