diff --git a/src/OpenSSL/SSL.py b/src/OpenSSL/SSL.py
index 5521151..adcfd8f 100644
--- a/src/OpenSSL/SSL.py
+++ b/src/OpenSSL/SSL.py
@@ -15,6 +15,7 @@
     UNSPECIFIED as _UNSPECIFIED,
     exception_from_error_queue as _exception_from_error_queue,
     ffi as _ffi,
+    from_buffer as _from_buffer,
     lib as _lib,
     make_assert as _make_assert,
     native as _native,
@@ -1730,18 +1731,18 @@
         # Backward compatibility
         buf = _text_to_bytes_and_warn("buf", buf)
 
-        if isinstance(buf, memoryview):
-            buf = buf.tobytes()
-        if isinstance(buf, _buffer):
-            buf = str(buf)
-        if not isinstance(buf, bytes):
-            raise TypeError("data must be a memoryview, buffer or byte string")
-        if len(buf) > 2147483647:
-            raise ValueError("Cannot send more than 2**31-1 bytes at once.")
+        with _from_buffer(buf) as data:
+            # check len(buf) instead of len(data) for testability
+            if len(buf) > 2147483647:
+                raise ValueError(
+                    "Cannot send more than 2**31-1 bytes at once."
+                )
 
-        result = _lib.SSL_write(self._ssl, buf, len(buf))
-        self._raise_ssl_error(self._ssl, result)
-        return result
+            result = _lib.SSL_write(self._ssl, data, len(data))
+            self._raise_ssl_error(self._ssl, result)
+
+            return result
+
     write = send
 
     def sendall(self, buf, flags=0):
@@ -1757,28 +1758,24 @@
         """
         buf = _text_to_bytes_and_warn("buf", buf)
 
-        if isinstance(buf, memoryview):
-            buf = buf.tobytes()
-        if isinstance(buf, _buffer):
-            buf = str(buf)
-        if not isinstance(buf, bytes):
-            raise TypeError("buf must be a memoryview, buffer or byte string")
+        with _from_buffer(buf) as data:
 
-        left_to_send = len(buf)
-        total_sent = 0
-        data = _ffi.new("char[]", buf)
+            left_to_send = len(buf)
+            total_sent = 0
 
-        while left_to_send:
-            # SSL_write's num arg is an int,
-            # so we cannot send more than 2**31-1 bytes at once.
-            result = _lib.SSL_write(
-                self._ssl,
-                data + total_sent,
-                min(left_to_send, 2147483647)
-            )
-            self._raise_ssl_error(self._ssl, result)
-            total_sent += result
-            left_to_send -= result
+            while left_to_send:
+                # SSL_write's num arg is an int,
+                # so we cannot send more than 2**31-1 bytes at once.
+                result = _lib.SSL_write(
+                    self._ssl,
+                    data + total_sent,
+                    min(left_to_send, 2147483647)
+                )
+                self._raise_ssl_error(self._ssl, result)
+                total_sent += result
+                left_to_send -= result
+
+            return total_sent
 
     def recv(self, bufsiz, flags=None):
         """
@@ -1892,10 +1889,11 @@
         if self._into_ssl is None:
             raise TypeError("Connection sock was not None")
 
-        result = _lib.BIO_write(self._into_ssl, buf, len(buf))
-        if result <= 0:
-            self._handle_bio_errors(self._into_ssl, result)
-        return result
+        with _from_buffer(buf) as data:
+            result = _lib.BIO_write(self._into_ssl, data, len(data))
+            if result <= 0:
+                self._handle_bio_errors(self._into_ssl, result)
+            return result
 
     def renegotiate(self):
         """
diff --git a/src/OpenSSL/_util.py b/src/OpenSSL/_util.py
index cdcacc8..d8e3f66 100644
--- a/src/OpenSSL/_util.py
+++ b/src/OpenSSL/_util.py
@@ -145,3 +145,17 @@
         )
         return obj.encode('utf-8')
     return obj
+
+
+try:
+    # newer versions of cffi free the buffer deterministically
+    with ffi.from_buffer(b""):
+        pass
+    from_buffer = ffi.from_buffer
+except AttributeError:
+    # cffi < 0.12 frees the buffer with refcounting gc
+    from contextlib import contextmanager
+
+    @contextmanager
+    def from_buffer(*args):
+        yield ffi.from_buffer(*args)