Fix for memory leak in RSA-SSA signing

Fix in mbedtls_rsa_rsassa_pkcs1_v15_sign() in rsa.c. Resolves github issue #372
diff --git a/ChangeLog b/ChangeLog
index b4cf598..cd7d5c9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,8 +7,10 @@
    * Fix bug in certificate validation that caused valid chains to be rejected
      when the first intermediate certificate has pathLenConstraint=0. Found by
      Nicholas Wilson. Introduced in mbed TLS 2.1.4. #280
+   * Removed potential leak in mbedtls_rsa_rsassa_pkcs1_v15_sign(), found by
+     JayaraghavendranK. #372
 
-Changes
+Change
    * To avoid dropping an entire DTLS datagram if a single record in a datagram
      is invalid, we now only drop the record and look at subsequent records (if
      any are present) in the same datagram to avoid interoperability issues.