Imported Upstream version 4.2.0.179

Former-commit-id: 0a113cb3a6feb7873f632839b1307cc6033cd595

mcs/class/System/System.IO.Compression/DeflateStream.cs

@@ -171,6 +171,9 @@ namespace System.IO.Compression
 			if (!CanWrite)
 				throw new NotSupportedException ("Stream does not support writing");
 
+			if (src_offset > src.Length - count)
+				throw new ArgumentException ("Buffer too small. count/offset wrong.");
+
 			WriteInternal (src, src_offset, count);
 		}