tls1_process_heartbeat: check for NULL after allocating buffer

Signed-off-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Matt Caswell <matt@openssl.org>

ssl/t1_lib.c

@@ -4003,6 +4003,11 @@ tls1_process_heartbeat(SSL *s)
 		 * payload, plus padding
 		 */
 		buffer = OPENSSL_malloc(1 + 2 + payload + padding);
+		if (buffer == NULL)
+			{
+			SSLerr(SSL_F_TLS1_PROCESS_HEARTBEAT,ERR_R_MALLOC_FAILURE);
+			return -1;
+			}
 		bp = buffer;
 		
 		/* Enter response type, length and copy payload */