Merge branch '5.5' into 10.0

mysql-test/r/connect_debug.result

+set @old_dbug=@@global.debug_dbug;
+set global debug_dbug='+d,auth_disconnect';
+create user 'bad' identified by 'worse';
+set global debug_dbug=@old_dbug;
+drop user bad;

mysql-test/t/connect_debug.test

+source include/have_debug.inc;
+set @old_dbug=@@global.debug_dbug;
+
+#
+# use after free if need plugin change and auth aborted
+#
+set global debug_dbug='+d,auth_disconnect';
+create user 'bad' identified by 'worse';
+--error 1
+--exec $MYSQL --default-auth=mysql_old_password --user=bad --password=worse
+set global debug_dbug=@old_dbug;
+drop user bad;

sql-common/client.c

@@ -1503,7 +1503,7 @@ MYSQL_DATA *cli_read_rows(MYSQL *mysql,MYSQL_FIELD *mysql_fields,
       else
       {
 	cur->data[field] = to;
-        if (to + len > end_to)
+        if (unlikely(len > (ulong)(end_to-to) || to > end_to))
         {
           free_rows(result);
           set_mysql_error(mysql, CR_MALFORMED_PACKET, unknown_sqlstate);
@@ -1575,7 +1575,7 @@ read_one_row(MYSQL *mysql,uint fields,MYSQL_ROW row, ulong *lengths)
     }
     else
     {
-      if (pos + len > end_pos)
+      if (unlikely(len > (ulong)(end_pos - pos) || pos > end_pos))
       {
         set_mysql_error(mysql, CR_UNKNOWN_ERROR, unknown_sqlstate);
         return -1;
@@ -2735,7 +2735,7 @@ static int client_mpvio_read_packet(struct st_plugin_vio *mpv, uchar **buf)
   *buf= mysql->net.read_pos;
 
   /* was it a request to change plugins ? */
-  if (**buf == 254)
+  if (pkt_len == packet_error || **buf == 254)
     return (int)packet_error; /* if yes, this plugin shan't continue */
 
   /*
@@ -2920,7 +2920,7 @@ int run_plugin_auth(MYSQL *mysql, char *data, uint data_len,
 
   compile_time_assert(CR_OK == -1);
   compile_time_assert(CR_ERROR == 0);
-  if (res > CR_OK && mysql->net.read_pos[0] != 254)
+  if (res > CR_OK && (mysql->net.last_errno || mysql->net.read_pos[0] != 254))
   {
     /*
       the plugin returned an error. write it down in mysql,

sql/sql_acl.cc

@@ -11172,6 +11172,7 @@ static bool send_plugin_request_packet(MPVIO_EXT *mpvio,
   const char *client_auth_plugin=
     ((st_mysql_auth *) (plugin_decl(mpvio->plugin)->info))->client_auth_plugin;
 
+  DBUG_EXECUTE_IF("auth_disconnect", { vio_close(net->vio); DBUG_RETURN(1); });
   DBUG_ASSERT(client_auth_plugin);
 
   /*