Fix potential double-free in ssl_conf_psk()

ChangeLog

diff --git a/ChangeLog b/ChangeLog
index aa96b18..0b6c20d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 mbed TLS ChangeLog (Sorted per branch, date)
 
+= mbed TLS 2.2.0 released 2015-10-xx
+
+Security
+   * Fix potential double free if mbedtls_ssl_conf_psk() is called more than
+     once and some allocation fails. Cannot be forced remotely. Found by Guido
+     Vranken, Intelworks.
+
 = mbed TLS 2.1.2 released 2015-10-06
 
 Security