Memory leak in row_log_table_apply_update(), in UPDATE involving BLOB, during online table rebuild

--source include/have_innodb.inc

CREATE TABLE t (pk INT PRIMARY KEY, f TEXT) ENGINE=InnoDB;

INSERT INTO t(pk) VALUES (1);

--connect (con1,localhost,root,,test)

--send

  ALTER TABLE t FORCE;

--connection default

DROP TABLE IF EXISTS non_existing;

UPDATE t SET f = REPEAT('a',10000);

--source include/restart_mysqld.inc

--connection default

DROP TABLE t;

==3197705==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 10 byte(s) in 1 object(s) allocated from:

    #0 0x7f66010bee8f in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145

    #1 0x56473333dc2c in rec_copy_prefix_to_buf(unsigned char const*, dict_index_t const*, unsigned long, unsigned char**, unsigned long*) /data/src/10.3/storage/innobase/rem/rem0rec.cc:2002

    #2 0x564733650dbe in btr_pcur_store_position(btr_pcur_t*, mtr_t*) /data/src/10.3/storage/innobase/btr/btr0pcur.cc:200

    #3 0x564733645c1c in btr_blob_log_check_t::check() /data/src/10.3/storage/innobase/btr/btr0cur.cc:7189

    #4 0x56473363e951 in btr_store_big_rec_extern_fields(btr_pcur_t*, unsigned short*, big_rec_t const*, mtr_t*, blob_op) /data/src/10.3/storage/innobase/btr/btr0cur.cc:7390

    #5 0x564733417aaf in row_log_table_apply_update /data/src/10.3/storage/innobase/row/row0log.cc:2327

    #6 0x56473341a4bc in row_log_table_apply_op /data/src/10.3/storage/innobase/row/row0log.cc:2669

    #7 0x56473341e8fa in row_log_table_apply_ops /data/src/10.3/storage/innobase/row/row0log.cc:3039

    #8 0x56473341f76e in row_log_table_apply(que_thr_t*, dict_table_t*, TABLE*, ut_stage_alter_t*, dict_table_t*) /data/src/10.3/storage/innobase/row/row0log.cc:3148

    #9 0x56473315f716 in ha_innobase::inplace_alter_table(TABLE*, Alter_inplace_info*) /data/src/10.3/storage/innobase/handler/handler0alter.cc:7223

    #10 0x56473264c815 in handler::ha_inplace_alter_table(TABLE*, Alter_inplace_info*) (/mnt8t/bld/10.3-asan-nightly/bin/mysqld+0x12a8815)

    #11 0x56473262fcf2 in mysql_inplace_alter_table /data/src/10.3/sql/sql_table.cc:7773

    #12 0x564732640afd in mysql_alter_table(THD*, st_mysql_const_lex_string const*, st_mysql_const_lex_string const*, HA_CREATE_INFO*, TABLE_LIST*, Alter_info*, unsigned int, st_order*, bool) /data/src/10.3/sql/sql_table.cc:10111

    #13 0x5647327a887b in Sql_cmd_alter_table::execute(THD*) /data/src/10.3/sql/sql_alter.cc:512

    #14 0x5647323f6745 in mysql_execute_command(THD*) /data/src/10.3/sql/sql_parse.cc:6076

    #15 0x5647324025fb in mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool) /data/src/10.3/sql/sql_parse.cc:7871

    #16 0x5647323d9ba1 in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool) /data/src/10.3/sql/sql_parse.cc:1852

    #17 0x5647323d677d in do_command(THD*) /data/src/10.3/sql/sql_parse.cc:1398

    #18 0x564732798159 in do_handle_one_connection(CONNECT*) /data/src/10.3/sql/sql_connect.cc:1403

    #19 0x564732797a55 in handle_one_connection /data/src/10.3/sql/sql_connect.cc:1308

    #20 0x564733d42ae6 in pfs_spawn_thread /data/src/10.3/storage/perfschema/pfs.cc:1869

    #21 0x7f660081cea6 in start_thread nptl/pthread_create.c:477

SUMMARY: AddressSanitizer: 10 byte(s) leaked in 1 allocation(s).