MSAN use-of-uninitialized-value errors in cmp_buffer_with_ref upon multi-table update

--source include/have_innodb.inc

CREATE TABLE t1 (id INT PRIMARY KEY, a VARCHAR(256)) ENGINE=InnoDB;

INSERT INTO t1 VALUES (1,'foo'),(2,'bar');

CREATE TABLE t2 (x INT) ENGINE=InnoDB;

INSERT INTO t2 VALUES (1);

UPDATE t1, t2 SET id = 4 WHERE a IN (SELECT 'baz' UNION SELECT 'qux');

# Cleanup

DROP TABLE t1, t2;

Uninitialized bytes in MemcmpInterceptorCommon at offset 6 inside [0x715000092f38, 259)

==72856==WARNING: MemorySanitizer: use-of-uninitialized-value

    #0 0x56542020c6fe in bcmp (/home/jenkins/10.5/sql/mariadbd+0x7196fe)

    #1 0x56542094e20c in cmp_buffer_with_ref(THD*, TABLE*, st_table_ref*) /home/jenkins/10.5/sql/sql_select.cc:24581:10

    #2 0x56542094e20c in join_read_key2(THD*, st_join_table*, TABLE*, st_table_ref*) /home/jenkins/10.5/sql/sql_select.cc:21577:7

    #3 0x565420e9ee27 in Expression_cache_tmptable::check_value(Item**) /home/jenkins/10.5/sql/sql_expression_cache.cc:221:15

    #4 0x56542144e414 in Item_cache_wrapper::check_cache() /home/jenkins/10.5/sql/item.cc:8783:22

    #5 0x56542144eced in Item_cache_wrapper::val_int() /home/jenkins/10.5/sql/item.cc:8846:22

    #6 0x56542094c27b in evaluate_join_record(JOIN*, st_join_table*, int) /home/jenkins/10.5/sql/sql_select.cc:21011:25

    #7 0x56542094a516 in sub_select(JOIN*, st_join_table*, bool) /home/jenkins/10.5/sql/sql_select.cc:20952:9

    #8 0x56542094cd31 in evaluate_join_record(JOIN*, st_join_table*, int) /home/jenkins/10.5/sql/sql_select.cc:21143:11

    #9 0x56542094a436 in sub_select(JOIN*, st_join_table*, bool) /home/jenkins/10.5/sql/sql_select.cc:20913:9

    #10 0x5654208c260a in do_select(JOIN*, Procedure*) /home/jenkins/10.5/sql/sql_select.cc:20445:14

    #11 0x5654208c260a in JOIN::exec_inner() /home/jenkins/10.5/sql/sql_select.cc:4538:50

    #12 0x5654208be50c in JOIN::exec() /home/jenkins/10.5/sql/sql_select.cc:4318:3

    #13 0x565420828c93 in mysql_select(THD*, TABLE_LIST*, List<Item>&, Item*, unsigned int, st_order*, st_order*, Item*, st_order*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*) /home/jenkins/10.5/sql/sql_select.cc:4795:9

    #14 0x565420b8011e in mysql_multi_update(THD*, TABLE_LIST*, List<Item>*, List<Item>*, Item*, unsigned long long, enum_duplicates, bool, st_select_lex_unit*, st_select_lex*, multi_update**) /home/jenkins/10.5/sql/sql_update.cc:1961:8

    #15 0x565420754216 in mysql_execute_command(THD*) /home/jenkins/10.5/sql/sql_parse.cc:4548:12

    #16 0x56542071f938 in mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool) /home/jenkins/10.5/sql/sql_parse.cc:8100:18

    #17 0x565420712bfc in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool) /home/jenkins/10.5/sql/sql_parse.cc:1891:7

    #18 0x5654207218ac in do_command(THD*) /home/jenkins/10.5/sql/sql_parse.cc:1370:17

    #19 0x565420d158d9 in do_handle_one_connection(CONNECT*, bool) /home/jenkins/10.5/sql/sql_connect.cc:1418:11

    #20 0x565420d14ff5 in handle_one_connection /home/jenkins/10.5/sql/sql_connect.cc:1312:5

    #21 0x5654221168ea in pfs_spawn_thread /home/jenkins/10.5/storage/perfschema/pfs.cc:2201:3

    #22 0x7f9f983b6608 in start_thread /build/glibc-eX1tMB/glibc-2.31/nptl/pthread_create.c:477:8

    #23 0x7f9f980bb292 in clone /build/glibc-eX1tMB/glibc-2.31/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95

  Uninitialized value was stored to memory at

    #0 0x565420202119 in __msan_memcpy (/home/jenkins/10.5/sql/mariadbd+0x70f119)

    #1 0x56542094e555 in cmp_buffer_with_ref(THD*, TABLE*, st_table_ref*) /home/jenkins/10.5/sql/sql_select.cc:24573:7

    #2 0x56542094e555 in join_read_key2(THD*, st_join_table*, TABLE*, st_table_ref*) /home/jenkins/10.5/sql/sql_select.cc:21577:7

  Uninitialized value was stored to memory at

    #0 0x565420202119 in __msan_memcpy (/home/jenkins/10.5/sql/mariadbd+0x70f119)

    #1 0x56542132f473 in field_conv_memcpy(Field*, Field*) /home/jenkins/10.5/sql/field_conv.cc:832:5

    #2 0x56542132f473 in field_conv(Field*, Field*) /home/jenkins/10.5/sql/field_conv.cc:862:10

  Memory was marked as uninitialized

    #0 0x5654202089ae in __msan_allocated_memory (/home/jenkins/10.5/sql/mariadbd+0x7159ae)

    #1 0x565422aec348 in row_sel_field_store_in_mysql_format_func(unsigned char*, mysql_row_templ_t const*, dict_index_t const*, unsigned long, unsigned char const*, unsigned long) /home/jenkins/10.5/storage/innobase/row/row0sel.cc:2755:2

SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/jenkins/10.5/sql/mariadbd+0x7196fe) in bcmp