ASAN heap-use-after-free in copy_if_not_alloced / copy_fields

SELECT REPLACE( CAST( CURDATE() AS BINARY ), CURDATE(), REPEAT('a',32) ) AS f FROM mysql.user GROUP BY f;

==3123==ERROR: AddressSanitizer: heap-use-after-free on address 0x60e000075750 at pc 0x55e95f17c4e7 bp 0x7f930d1b0a80 sp 0x7f930d1b0a78

READ of size 10 at 0x60e000075750 thread T6

    #0 0x55e95f17c4e6 in copy_if_not_alloced(String*, String*, unsigned int) /data/src/10.1/sql/sql_string.cc:915

    #1 0x55e95f68d9f5 in Item_func_replace::val_str(String*) /data/src/10.1/sql/item_strfunc.cc:1197

    #2 0x55e95f536641 in Item_copy_string::copy() /data/src/10.1/sql/item.cc:4063

    #3 0x55e95f0c1fdb in copy_fields(TMP_TABLE_PARAM*) /data/src/10.1/sql/sql_select.cc:23163

    #4 0x55e95f0d0115 in end_send_group(JOIN*, st_join_table*, bool) /data/src/10.1/sql/sql_select.cc:19816

    #5 0x55e95f0657b2 in evaluate_join_record /data/src/10.1/sql/sql_select.cc:18702

    #6 0x55e95f0813fd in sub_select(JOIN*, st_join_table*, bool) /data/src/10.1/sql/sql_select.cc:18479

    #7 0x55e95f0ba9d0 in do_select /data/src/10.1/sql/sql_select.cc:18134

    #8 0x55e95f0ff54e in JOIN::exec_inner() /data/src/10.1/sql/sql_select.cc:3275

    #9 0x55e95f100836 in JOIN::exec() /data/src/10.1/sql/sql_select.cc:2562

    #10 0x55e95f0f5089 in mysql_select(THD*, Item***, TABLE_LIST*, unsigned int, List<Item>&, Item*, unsigned int, st_order*, st_order*, Item*, st_order*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*) /data/src/10.1/sql/sql_select.cc:3499

    #11 0x55e95f0f5877 in handle_select(THD*, LEX*, select_result*, unsigned long) /data/src/10.1/sql/sql_select.cc:388

    #12 0x55e95efc4a59 in execute_sqlcom_select /data/src/10.1/sql/sql_parse.cc:5950

    #13 0x55e95efdec69 in mysql_execute_command(THD*) /data/src/10.1/sql/sql_parse.cc:2995

    #14 0x55e95eff6e7a in mysql_parse(THD*, char*, unsigned int, Parser_state*) /data/src/10.1/sql/sql_parse.cc:7468

    #15 0x55e95effdc5e in dispatch_command(enum_server_command, THD*, char*, unsigned int) /data/src/10.1/sql/sql_parse.cc:1496

    #16 0x55e95f0043ea in do_command(THD*) /data/src/10.1/sql/sql_parse.cc:1124

    #17 0x55e95f2ac8bf in do_handle_one_connection(THD*) /data/src/10.1/sql/sql_connect.cc:1330

    #18 0x55e95f2acdd0 in handle_one_connection /data/src/10.1/sql/sql_connect.cc:1242

    #19 0x55e95fb7bccc in pfs_spawn_thread /data/src/10.1/storage/perfschema/pfs.cc:1861

    #20 0x7f93198e7493 in start_thread (/lib/x86_64-linux-gnu/libpthread.so.0+0x7493)

    #21 0x7f9317ca093e in __clone (/lib/x86_64-linux-gnu/libc.so.6+0xe893e)

0x60e000075750 is located 112 bytes inside of 148-byte region [0x60e0000756e0,0x60e000075774)

freed by thread T6 here:

    #0 0x7f9319b51527 in __interceptor_free (/usr/lib/x86_64-linux-gnu/libasan.so.1+0x54527)

    #1 0x55e9603480e1 in free_memory /data/src/10.1/mysys/safemalloc.c:276

previously allocated by thread T6 here:

    #0 0x7f9319b5173f in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.1+0x5473f)

    #1 0x55e9603481b2 in sf_malloc /data/src/10.1/mysys/safemalloc.c:115

    #2 0x55e960440c1a (/data/bld/10.1-asan/bin/mysqld+0x1d9ec1a)

Thread T6 created by T0 here:

    #0 0x7f9319b20bba in pthread_create (/usr/lib/x86_64-linux-gnu/libasan.so.1+0x23bba)

    #1 0x55e95fb87523 in spawn_thread_v1 /data/src/10.1/storage/perfschema/pfs.cc:1911

SUMMARY: AddressSanitizer: heap-use-after-free /data/src/10.1/sql/sql_string.cc:915 copy_if_not_alloced(String*, String*, unsigned int)

Shadow bytes around the buggy address:

  0x0c1c80006a90: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

  0x0c1c80006aa0: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00

  0x0c1c80006ab0: 00 00 00 00 00 00 00 04 fa fa fa fa fa fa fa fa

  0x0c1c80006ac0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

  0x0c1c80006ad0: 00 00 04 fa fa fa fa fa fa fa fa fa fd fd fd fd

=>0x0c1c80006ae0: fd fd fd fd fd fd fd fd fd fd[fd]fd fd fd fd fa

  0x0c1c80006af0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00

  0x0c1c80006b00: 00 00 00 00 00 00 00 00 00 00 02 04 fa fa fa fa

  0x0c1c80006b10: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00

  0x0c1c80006b20: 00 00 00 00 00 01 04 fa fa fa fa fa fa fa fa fa

  0x0c1c80006b30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Shadow byte legend (one shadow byte represents 8 application bytes):

  Addressable:           00

  Partially addressable: 01 02 03 04 05 06 07 

  Heap left redzone:       fa

  Heap right redzone:      fb

  Freed heap region:       fd

  Stack left redzone:      f1

  Stack mid redzone:       f2

  Stack right redzone:     f3

  Stack partial redzone:   f4

  Stack after return:      f5

  Stack use after scope:   f8

  Global redzone:          f9

  Global init order:       f6

  Poisoned by user:        f7

  Contiguous container OOB:fc

  ASan internal:           fe

==3123==ABORTING