MSAN use-of-uninitialized-value in READ_INFO::read_xml()

CURRENT_TEST: main.loadxml

mysqltest: At line 16: query 'load xml infile '../../std_data/loadxml.dat' into table t1

rows identified by '<row>'' failed: 2013: Lost connection to MySQL server during query

…

Version: '10.5.4-MariaDB-debug-log'  socket: '/dev/shm/10.5-msan/mysql-test/var/tmp/2/mysqld.1.sock'  port: 16000  Source distribution

Uninitialized bytes in MemcmpInterceptorCommon at offset 4 inside [0x70a00000b058, 5)

==401652==WARNING: MemorySanitizer: use-of-uninitialized-value

    #0 0x55767f9b2f7c in bcmp (/dev/shm/10.5-msan/sql/mariadbd+0x70cf7c)

    #1 0x55767fee18e1 in READ_INFO::read_xml(THD*) /mariadb/10.5m/sql/sql_load.cc:2032:11

    #2 0x55767fec2974 in read_xml_field(THD*, st_copy_info&, TABLE_LIST*, List<Item>&, List<Item>&, List<Item>&, READ_INFO&, String&, unsigned long, bool) /mariadb/10.5m/sql/sql_load.cc:1227:19

    #3 0x55767fec2974 in mysql_load(THD*, sql_exchange const*, TABLE_LIST*, List<Item>&, List<Item>&, List<Item>&, enum_duplicates, bool, bool) /mariadb/10.5m/sql/sql_load.cc:669:14

    #4 0x55767ff1e7dd in mysql_execute_command(THD*) /mariadb/10.5m/sql/sql_parse.cc:5001:10

    #5 0x55767ff012f5 in mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool) /mariadb/10.5m/sql/sql_parse.cc:7991:18

    #6 0x55767fef1c79 in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool) /mariadb/10.5m/sql/sql_parse.cc:1874:7

    #7 0x55767ff031ba in do_command(THD*) /mariadb/10.5m/sql/sql_parse.cc:1355:17

    #8 0x55768051f2be in do_handle_one_connection(CONNECT*, bool) /mariadb/10.5m/sql/sql_connect.cc:1411:11

    #9 0x55768051eaa4 in handle_one_connection /mariadb/10.5m/sql/sql_connect.cc:1313:5

    #10 0x5576819c92c7 in pfs_spawn_thread /mariadb/10.5m/storage/perfschema/pfs.cc:2201:3

    #11 0x7fd8ba1bef26 in start_thread nptl/pthread_create.c:479:8

    #12 0x7fd8b9c9d31e in clone misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95

  Memory was marked as uninitialized

    #0 0x55767f9af28e in __msan_allocated_memory (/dev/shm/10.5-msan/sql/mariadbd+0x70928e)

    #1 0x55768306b237 in my_malloc /mariadb/10.5m/mysys/my_malloc.c:111:7

    case '=': /* attribute name end - read the value */

      //check for tag field and attribute name

      if(!memcmp(tag.c_ptr_safe(), STRING_WITH_LEN("field")) &&

         !memcmp(attribute.c_ptr_safe(), STRING_WITH_LEN("name")))