MDEV#6411 - Setting set @@global_wsrep_sst_auth=NULL

causes crash

Fixed by properly handling the NULL values.

mysql-test/suite/wsrep/r/variables.result

@@ -11,6 +11,7 @@ SET SESSION wsrep_replicate_myisam= ON;
 ERROR HY000: Variable 'wsrep_replicate_myisam' is a GLOBAL variable and should be set with SET GLOBAL
 SET GLOBAL wsrep_replicate_myisam= ON;
 SET GLOBAL wsrep_replicate_myisam= OFF;
+SET GLOBAL wsrep_provider=none;
 
 #
 # MDEV#6206: wsrep_slave_threads subtracts from max_connections
@@ -76,4 +77,21 @@ SET GLOBAL wsrep_slave_threads= @wsrep_slave_threads_saved;
 SET GLOBAL wsrep_provider= none;
 SET GLOBAL wsrep_cluster_address= '';
 SET GLOBAL wsrep_provider_options= '';
+#
+# MDEV#6411: Setting set @@global.wsrep_sst_auth=NULL causes crash
+#
+SET @wsrep_sst_auth_saved= @@global.wsrep_sst_auth;
+SET @@global.wsrep_sst_auth= 'user:pass';
+SELECT @@global.wsrep_sst_auth;
+@@global.wsrep_sst_auth
+********
+SET @@global.wsrep_sst_auth= '';
+SELECT @@global.wsrep_sst_auth;
+@@global.wsrep_sst_auth
+
+SET @@global.wsrep_sst_auth= NULL;
+SELECT @@global.wsrep_sst_auth;
+@@global.wsrep_sst_auth
+NULL
+SET @@global.wsrep_sst_auth= @wsrep_sst_auth_saved;
 # End of test.

mysql-test/suite/wsrep/t/variables.test

@@ -19,6 +19,7 @@ SET GLOBAL wsrep_replicate_myisam= ON;
 
 # Reset it back.
 SET GLOBAL wsrep_replicate_myisam= OFF;
+SET GLOBAL wsrep_provider=none;
 
 --echo
 --echo #
@@ -26,6 +27,11 @@ SET GLOBAL wsrep_replicate_myisam= OFF;
 --echo #
 call mtr.add_suppression("safe_mutex: Found wrong usage of mutex 'LOCK_wsrep_slave_threads' and 'LOCK_global_system_variables'");
 call mtr.add_suppression("WSREP: Failed to get provider options");
+
+--disable_query_log
+eval SET GLOBAL wsrep_provider= '$WSREP_PROVIDER';
+--enable_query_log
+
 --replace_regex /.*libgalera_smm.*/libgalera_smm.so/
 SELECT @@global.wsrep_provider;
 SELECT @@global.wsrep_slave_threads;
@@ -71,5 +77,17 @@ SET GLOBAL wsrep_provider= none;
 SET GLOBAL wsrep_cluster_address= '';
 SET GLOBAL wsrep_provider_options= '';
 
+--echo #
+--echo # MDEV#6411: Setting set @@global.wsrep_sst_auth=NULL causes crash
+--echo #
+SET @wsrep_sst_auth_saved= @@global.wsrep_sst_auth;
+SET @@global.wsrep_sst_auth= 'user:pass';
+SELECT @@global.wsrep_sst_auth;
+SET @@global.wsrep_sst_auth= '';
+SELECT @@global.wsrep_sst_auth;
+SET @@global.wsrep_sst_auth= NULL;
+SELECT @@global.wsrep_sst_auth;
+SET @@global.wsrep_sst_auth= @wsrep_sst_auth_saved;
+
 --echo # End of test.
 

sql/mysqld.cc

@@ -1759,7 +1759,7 @@ static void __cdecl kill_server(int sig_ptr)
   close_connections();
 #ifdef WITH_WSREP
   if (wsrep_inited == 1)
-    wsrep_deinit();
+    wsrep_deinit(true);
 #endif
   if (sig != MYSQL_KILL_SIGNAL &&
       sig != 0)
@@ -1871,7 +1871,7 @@ extern "C" void unireg_abort(int exit_code)
 
     /* In bootstrap mode we deinitialize wsrep here. */
     if (opt_bootstrap && wsrep_inited)
-      wsrep_deinit();
+      wsrep_deinit(true);
   }
 #endif // WITH_WSREP
 

sql/wsrep_mysqld.cc

@@ -696,7 +696,7 @@ void wsrep_init_startup (bool first)
 }
 
 
-void wsrep_deinit()
+void wsrep_deinit(bool free_options)
 {
   DBUG_ASSERT(wsrep_inited == 1);
   wsrep_unload(wsrep);
@@ -708,6 +708,11 @@ void wsrep_deinit()
   delete wsrep_format_desc;
   wsrep_format_desc= NULL;
   wsrep_inited= 0;
+
+  if (free_options)
+  {
+    wsrep_sst_auth_free();
+  }
 }
 
 void wsrep_recover()

sql/wsrep_mysqld.h

@@ -124,7 +124,7 @@ void wsrep_free_status(THD *thd);
 void wsrep_filter_new_cluster (int* argc, char* argv[]);
 
 int  wsrep_init();
-void wsrep_deinit();
+void wsrep_deinit(bool free_options);
 void wsrep_recover();
 bool wsrep_before_SE(); // initialize wsrep before storage
                         // engines (true) or after (false)

sql/wsrep_sst.cc

@@ -120,31 +120,44 @@ bool wsrep_sst_auth_check (sys_var *self, THD* thd, set_var* var)
 {
     return 0;
 }
+
 static bool sst_auth_real_set (const char* value)
 {
-    const char* v = strdup (value);
+  const char* v= NULL;
 
-    if (v)
+  if (value)
+  {
+    v= my_strdup(value, MYF(0));
+  }
+  else                                          // its NULL
+  {
+    wsrep_sst_auth_free();
+    return 0;
+  }
+
+  if (v)
+  {
+    // set sst_auth_real
+    if (sst_auth_real) { my_free((void *) sst_auth_real); }
+    sst_auth_real = v;
+
+    // mask wsrep_sst_auth
+    if (strlen(sst_auth_real))
     {
-        if (sst_auth_real) free (const_cast<char*>(sst_auth_real));
+      if (wsrep_sst_auth) { my_free((void*) wsrep_sst_auth); }
-        sst_auth_real = v;
+      wsrep_sst_auth= my_strdup(WSREP_SST_AUTH_MASK, MYF(0));
-
-        if (strlen(sst_auth_real))
-        {
-          if (wsrep_sst_auth)
-          {
-            my_free ((void*)wsrep_sst_auth);
-            wsrep_sst_auth = my_strdup(WSREP_SST_AUTH_MASK, MYF(0));
-            //strncpy (wsrep_sst_auth, WSREP_SST_AUTH_MASK,
-            //     sizeof(wsrep_sst_auth) - 1);
-          }
-          else
-            wsrep_sst_auth = my_strdup (WSREP_SST_AUTH_MASK, MYF(0));
-        }
-        return 0;
     }
+    return 0;
+  }
+  return 1;
+}
 
-    return 1;
+void wsrep_sst_auth_free()
+{
+  if (wsrep_sst_auth) { my_free((void *) wsrep_sst_auth); }
+  if (sst_auth_real) { my_free((void *) sst_auth_real); }
+  wsrep_sst_auth= NULL;
+  sst_auth_real= NULL;
 }
 
 bool wsrep_sst_auth_update (sys_var *self, THD* thd, enum_var_type type)

sql/wsrep_sst.h

@@ -31,6 +31,7 @@ extern void wsrep_sst_grab();
 extern bool wsrep_sst_wait();
 /*! Signals wsrep that initialization is complete, writesets can be applied */
 extern void wsrep_sst_continue();
+extern void wsrep_sst_auth_free();
 
 extern void wsrep_SE_init_grab();   /*! grab init critical section */
 extern void wsrep_SE_init_wait();   /*! wait for SE init to complete */

sql/wsrep_var.cc

@@ -239,7 +239,7 @@ bool wsrep_provider_update (sys_var *self, THD* thd, enum_var_type type)
   mysql_mutex_lock(&LOCK_global_system_variables);
 
   if (wsrep_inited == 1)
-    wsrep_deinit();
+    wsrep_deinit(false);
 
   char* tmp= strdup(wsrep_provider); // wsrep_init() rewrites provider 
                                      //when fails