Merge remote-tracking branch 'public/pr/1161' into mbedtls-1.3

* public/pr/1161:
  Address PR review comments
  Backport 1.3:Fix crash when calling `mbedtls_ssl_cache_free` twice

ChangeLog

@@ -38,6 +38,8 @@ Bugfix
    * Add a check for invalid private parameters in ecdsa_sign.
      Reported by Yolan Romailler.
    * Fix word size check in in pk.c to not depend on MBEDTLS_HAVE_INT64.
+   * Fix crash when calling mbedtls_ssl_cache_free() twice. Found by
+     MilenkoMitrovic, #1104
 
 Changes
    * Extend cert_write example program by options to set the CRT version

library/ssl_cache.c

@@ -324,6 +324,8 @@ void ssl_cache_free( ssl_cache_context *cache )
 #if defined(POLARSSL_THREADING_C)
     polarssl_mutex_free( &cache->mutex );
 #endif
+
+    cache->chain = NULL;
 }
 
 #endif /* POLARSSL_SSL_CACHE_C */