SSL initialization calls RAND_load_file() which needs stat() enabled.

Index: vsftpd-3.0.3/seccompsandbox.c
===================================================================
--- vsftpd-3.0.3.orig/seccompsandbox.c	2021-12-21 15:33:01.491786690 +0100
+++ vsftpd-3.0.3/seccompsandbox.c	2021-12-21 15:33:01.499786535 +0100
@@ -559,6 +559,8 @@ seccomp_sandbox_setup_postlogin_broker()
     allow_nr(__NR_fstat);
     allow_nr(__NR_fchown);
     allow_nr_1_arg_match(__NR_recvmsg, 3, 0);
+    // called by RAND_load_file
+    allow_nr(__NR_stat);
   }
   if (tunable_syslog_enable)
   {