ASAN heap-use-after-free in String::copy / get_field_default_value

CREATE TABLE t (a BLOB DEFAULT 'x');

CREATE VIEW v AS SELECT * FROM t;

INSERT INTO t () VALUES ();

UPDATE t SET a = DEFAULT;

SELECT * FROM information_schema.columns WHERE table_name = 'v';

# Cleanup

DROP VIEW v;

DROP TABLE t;

==3075970==ERROR: AddressSanitizer: heap-use-after-free on address 0x602000004398 at pc 0x7f8a43182983 bp 0x7f8a3806c170 sp 0x7f8a3806b920

READ of size 1 at 0x602000004398 thread T5

    #0 0x7f8a43182982 in __interceptor_memcpy ../../../../src/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:806

    #1 0x55a15aec676a in String::copy(char const*, unsigned long, charset_info_st const*) /data/src/10.2/sql/sql_string.cc:200

    #2 0x55a15aec7179 in String::copy(char const*, unsigned int, charset_info_st const*, charset_info_st const*, unsigned int*) /data/src/10.2/sql/sql_string.cc:387

    #3 0x55a15ae5dc2c in get_field_default_value /data/src/10.2/sql/sql_show.cc:1823

    #4 0x55a15ae7f57f in get_schema_column_record /data/src/10.2/sql/sql_show.cc:5740

    #5 0x55a15ae60b9a in fill_schema_table_by_open /data/src/10.2/sql/sql_show.cc:4475

    #6 0x55a15ae9a429 in get_all_tables(THD*, TABLE_LIST*, Item*) /data/src/10.2/sql/sql_show.cc:5101

    #7 0x55a15aea14f3 in get_schema_tables_result(JOIN*, enum_schema_table_state) /data/src/10.2/sql/sql_show.cc:8573

    #8 0x55a15ae499a4 in JOIN::exec_inner() /data/src/10.2/sql/sql_select.cc:3615

    #9 0x55a15ae4bc79 in JOIN::exec() /data/src/10.2/sql/sql_select.cc:3446

    #10 0x55a15ae4c073 in mysql_select(THD*, 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/10.2/sql/sql_select.cc:3849

    #11 0x55a15ae4ea7a in handle_select(THD*, LEX*, select_result*, unsigned long) /data/src/10.2/sql/sql_select.cc:361

    #12 0x55a15acf49a7 in execute_sqlcom_select /data/src/10.2/sql/sql_parse.cc:6271

    #13 0x55a15ad1aee1 in mysql_execute_command(THD*) /data/src/10.2/sql/sql_parse.cc:3582

    #14 0x55a15ad23747 in mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool) /data/src/10.2/sql/sql_parse.cc:7793

    #15 0x55a15ad29b8e in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool) /data/src/10.2/sql/sql_parse.cc:1827

    #16 0x55a15ad2da2d in do_command(THD*) /data/src/10.2/sql/sql_parse.cc:1381

    #17 0x55a15b0109f6 in do_handle_one_connection(CONNECT*) /data/src/10.2/sql/sql_connect.cc:1336

    #18 0x55a15b01112a in handle_one_connection /data/src/10.2/sql/sql_connect.cc:1241

    #19 0x55a15c1a2324 in pfs_spawn_thread /data/src/10.2/storage/perfschema/pfs.cc:1869

    #20 0x7f8a42c7bea6 in start_thread nptl/pthread_create.c:477

    #21 0x7f8a42880dee in __clone (/lib/x86_64-linux-gnu/libc.so.6+0xfddee)

0x602000004398 is located 8 bytes inside of 16-byte region [0x602000004390,0x6020000043a0)

freed by thread T5 here:

    #0 0x7f8a431f2b6f in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:123

    #1 0x55a15b2689d5 in String::free() /data/src/10.2/sql/sql_string.h:351

    #2 0x55a15b2689d5 in String::~String() /data/src/10.2/sql/sql_string.h:187

    #3 0x55a15b2689d5 in Field_blob::~Field_blob() /data/src/10.2/sql/field.h:3308

    #4 0x55a15b2689d5 in Field_blob::~Field_blob() /data/src/10.2/sql/field.h:3308

    #5 0x55a15b2b67fa in Item_default_value::cleanup() /data/src/10.2/sql/item.cc:9064

    #6 0x55a15ac5bf33 in Item::delete_self() /data/src/10.2/sql/item.h:1964

    #7 0x55a15ac5bf33 in Query_arena::free_items() /data/src/10.2/sql/sql_class.cc:3642

    #8 0x55a15ac63532 in THD::cleanup_after_query() /data/src/10.2/sql/sql_class.cc:2097

    #9 0x55a15ad2337e in mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool) /data/src/10.2/sql/sql_parse.cc:7815

    #10 0x55a15ad29b8e in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool) /data/src/10.2/sql/sql_parse.cc:1827

    #11 0x55a15ad2da2d in do_command(THD*) /data/src/10.2/sql/sql_parse.cc:1381

    #12 0x55a15b0109f6 in do_handle_one_connection(CONNECT*) /data/src/10.2/sql/sql_connect.cc:1336

    #13 0x55a15b01112a in handle_one_connection /data/src/10.2/sql/sql_connect.cc:1241

    #14 0x55a15c1a2324 in pfs_spawn_thread /data/src/10.2/storage/perfschema/pfs.cc:1869

    #15 0x7f8a42c7bea6 in start_thread nptl/pthread_create.c:477

previously allocated by thread T5 here:

    #0 0x7f8a431f2e8f in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145

    #1 0x55a15c25a9a2 in my_malloc /data/src/10.2/mysys/my_malloc.c:101

    #2 0x55a15aec5e23 in String::real_alloc(unsigned long) /data/src/10.2/sql/sql_string.cc:45

    #3 0x55a15b25d98c in String::alloc(unsigned long) /data/src/10.2/sql/sql_string.h:361

    #4 0x55a15b25d98c in Field_blob::store(char const*, unsigned int, charset_info_st const*) /data/src/10.2/sql/field.cc:8305

    #5 0x55a15b2239b3 in Field::set_default() /data/src/10.2/sql/field.cc:2457

    #6 0x55a15b2f8c72 in Item_default_value::save_in_field(Field*, bool) /data/src/10.2/sql/item.cc:9133

    #7 0x55a15ac2c516 in fill_record(THD*, TABLE*, List<Item>&, List<Item>&, bool, bool) /data/src/10.2/sql/sql_base.cc:8118

    #8 0x55a15ac2d2b9 in fill_record_n_invoke_before_triggers(THD*, TABLE*, List<Item>&, List<Item>&, bool, trg_event_type) /data/src/10.2/sql/sql_base.cc:8263

    #9 0x55a15af4f7ed in mysql_update(THD*, TABLE_LIST*, List<Item>&, List<Item>&, Item*, unsigned int, st_order*, unsigned long long, enum_duplicates, bool, unsigned long long*, unsigned long long*) /data/src/10.2/sql/sql_update.cc:766

    #10 0x55a15ad15ddd in mysql_execute_command(THD*) /data/src/10.2/sql/sql_parse.cc:4056

    #11 0x55a15ad23747 in mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool) /data/src/10.2/sql/sql_parse.cc:7793

    #12 0x55a15ad29b8e in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool) /data/src/10.2/sql/sql_parse.cc:1827

    #13 0x55a15ad2da2d in do_command(THD*) /data/src/10.2/sql/sql_parse.cc:1381

    #14 0x55a15b0109f6 in do_handle_one_connection(CONNECT*) /data/src/10.2/sql/sql_connect.cc:1336

    #15 0x55a15b01112a in handle_one_connection /data/src/10.2/sql/sql_connect.cc:1241

    #16 0x55a15c1a2324 in pfs_spawn_thread /data/src/10.2/storage/perfschema/pfs.cc:1869

    #17 0x7f8a42c7bea6 in start_thread nptl/pthread_create.c:477

Thread T5 created by T0 here:

    #0 0x7f8a4319e2a2 in __interceptor_pthread_create ../../../../src/libsanitizer/asan/asan_interceptors.cpp:214

    #1 0x55a15c1a75aa in spawn_thread_v1 /data/src/10.2/storage/perfschema/pfs.cc:1919

    #2 0x55a15ab1eecf in inline_mysql_thread_create /data/src/10.2/include/mysql/psi/mysql_thread.h:1246

    #3 0x55a15ab1eecf in create_thread_to_handle_connection(CONNECT*) /data/src/10.2/sql/mysqld.cc:6580

    #4 0x55a15ab2f26c in create_new_thread /data/src/10.2/sql/mysqld.cc:6650

    #5 0x55a15ab2f26c in handle_connections_sockets() /data/src/10.2/sql/mysqld.cc:6908

    #6 0x55a15ab3179f in mysqld_main(int, char**) /data/src/10.2/sql/mysqld.cc:6199

    #7 0x7f8a427a9d09 in __libc_start_main ../csu/libc-start.c:308

SUMMARY: AddressSanitizer: heap-use-after-free ../../../../src/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:806 in __interceptor_memcpy

Shadow bytes around the buggy address:

  0x0c047fff8820: fa fa fd fd fa fa fd fd fa fa fd fd fa fa fd fd

  0x0c047fff8830: fa fa fd fd fa fa fd fd fa fa fd fd fa fa 00 00

  0x0c047fff8840: fa fa 00 00 fa fa fd fd fa fa 00 00 fa fa 00 00

  0x0c047fff8850: fa fa 00 00 fa fa 00 00 fa fa 00 00 fa fa fd fd

  0x0c047fff8860: fa fa fd fd fa fa fd fd fa fa 00 00 fa fa 00 00

=>0x0c047fff8870: fa fa fd[fd]fa fa 00 00 fa fa fa fa fa fa fa fa

  0x0c047fff8880: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

  0x0c047fff8890: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

  0x0c047fff88a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

  0x0c047fff88b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

  0x0c047fff88c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

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

  Freed heap region:       fd

  Stack left redzone:      f1

  Stack mid redzone:       f2

  Stack right redzone:     f3

  Stack after return:      f5

  Stack use after scope:   f8

  Global redzone:          f9

  Global init order:       f6

  Poisoned by user:        f7

  Container overflow:      fc

  Array cookie:            ac

  Intra object redzone:    bb

  ASan internal:           fe

  Left alloca redzone:     ca

  Right alloca redzone:    cb

  Shadow gap:              cc

==3075970==ABORTING