Overrun buffer in to_string_native()

CREATE TABLE t1 (a DECIMAL(15,11) ZEROFILL);

INSERT INTO t1 (a) VALUES (0.1),(0.2);

SELECT ENCRYPT(a) AS f, COUNT(*) FROM t1 GROUP BY f;

# Cleanup

DROP TABLE t1;

'SELECT ENCRYPT(a) AS f, COUNT(*) FROM t1 GROUP BY f' failed: <Unknown> (5): Out of memory (Needed 24 bytes)

Error: Reallocating overrun buffer 0x60e00002c570 at mysys/safemalloc.c:352, mysys/safemalloc.c:185, mysys/my_malloc.c:151, sql/sql_string.cc:98, sql/sql_string.h:703, sql/sql_string.h:669, sql/item_strfunc.cc:2281, sql/item.cc:6663

Allocated at mysys/my_malloc.c:90, sql/sql_string.cc:104, sql/sql_string.h:703, sql/sql_string.cc:229, sql/sql_string.h:879, sql/item_strfunc.cc:2290, sql/item.cc:6663, sql/sql_type.cc:4324

Error: Freeing overrun buffer 0x60e00002c570 at mysys/safemalloc.c:352, mysys/safemalloc.c:200, mysys/my_malloc.c:212, sql/sql_string.h:228, sql/sql_string.h:459, sql/sql_string.h:467, sql/sql_string.h:819, sql/item_strfunc.cc:2289

Allocated at mysys/my_malloc.c:90, sql/sql_string.cc:104, sql/sql_string.h:703, sql/sql_string.cc:229, sql/sql_string.h:879, sql/item_strfunc.cc:2290, sql/item.cc:6663, sql/sql_type.cc:4324

==1788135== Invalid write of size 1

==1788135==    at 0x17C4DFB: decimal2string (decimal.c:395)

==1788135==    by 0xF7063B: my_decimal::to_string_native(String*, unsigned int, unsigned int, char, unsigned int) const (my_decimal.cc:120)

==1788135==    by 0x9078FE: my_decimal::to_string(String*, unsigned int, unsigned int, char) const (my_decimal.h:218)

==1788135==    by 0xBE0280: Field_new_decimal::val_str(String*, String*) (field.h:2403)

==1788135==    by 0xDFE677: Item_field::val_str(String*) (item.cc:3277)

==1788135==    by 0xEAC112: Item_func_encrypt::val_str(String*) (item_strfunc.cc:2259)

==1788135==    by 0xE0907C: Item::save_str_in_field(Field*, bool) (item.cc:6663)

==1788135==    by 0xCAA6C9: Type_handler_string_result::Item_save_in_field(Item*, Field*, bool) const (sql_type.cc:4323)

==1788135==    by 0xE093CC: Item::save_in_field(Field*, bool) (item.cc:6711)

==1788135==    by 0x9A43FD: Item_result_field::save_in_result_field(bool) (item.h:3406)

==1788135==    by 0xAD627C: copy_funcs(Item**, THD const*) (sql_select.cc:26168)

==1788135==    by 0xACCDA0: end_update(JOIN*, st_join_table*, bool) (sql_select.cc:22562)

==1788135==    by 0xADFC6F: AGGR_OP::put_record(bool) (sql_select.cc:29317)

==1788135==    by 0xAE7B04: AGGR_OP::put_record() (sql_select.h:1056)

==1788135==    by 0xAC841B: sub_select_postjoin_aggr(JOIN*, st_join_table*, bool) (sql_select.cc:20710)

==1788135==    by 0xAC9101: evaluate_join_record(JOIN*, st_join_table*, int) (sql_select.cc:21217)

==1788135==  Address 0xc3ec408 is 0 bytes after a block of size 40 alloc'd

==1788135==    at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)

==1788135==    by 0x1754683: my_malloc (my_malloc.c:90)

==1788135==    by 0xB2D224: Binary_string::realloc_raw(unsigned long) (sql_string.cc:104)

==1788135==    by 0x8F55C0: Binary_string::realloc(unsigned long) (sql_string.h:703)

==1788135==    by 0xB2D911: Binary_string::copy() (sql_string.cc:229)

==1788135==    by 0xCCF261: String::copy() (sql_string.h:878)

==1788135==    by 0xEAC395: Item_func_encrypt::val_str(String*) (item_strfunc.cc:2289)

==1788135==    by 0xE0907C: Item::save_str_in_field(Field*, bool) (item.cc:6663)

==1788135==    by 0xCAA6C9: Type_handler_string_result::Item_save_in_field(Item*, Field*, bool) const (sql_type.cc:4323)

==1788135==    by 0xE093CC: Item::save_in_field(Field*, bool) (item.cc:6711)

==1788135==    by 0x90AF4B: Item::save_org_in_field(Field*, int (*)(Field*, Field*)) (item.h:1198)

==1788135==    by 0xACCC26: end_update(JOIN*, st_join_table*, bool) (sql_select.cc:22540)

==1788135==    by 0xADFC6F: AGGR_OP::put_record(bool) (sql_select.cc:29317)

==1788135==    by 0xAE7B04: AGGR_OP::put_record() (sql_select.h:1056)

==1788135==    by 0xAC841B: sub_select_postjoin_aggr(JOIN*, st_join_table*, bool) (sql_select.cc:20710)

==1788135==    by 0xAC9101: evaluate_join_record(JOIN*, st_join_table*, int) (sql_select.cc:21217)

==1788135== Conditional jump or move depends on uninitialised value(s)

==1788135==    at 0x483EF58: strlen (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)

==1788135==    by 0x48794BE: ??? (in /usr/lib/x86_64-linux-gnu/libcrypt.so.1.1.0)

==1788135==    by 0x48796E0: crypt_r (in /usr/lib/x86_64-linux-gnu/libcrypt.so.1.1.0)

==1788135==    by 0xEAC329: Item_func_encrypt::val_str(String*) (item_strfunc.cc:2281)

==1788135==    by 0xE0907C: Item::save_str_in_field(Field*, bool) (item.cc:6663)

==1788135==    by 0xCAA6C9: Type_handler_string_result::Item_save_in_field(Item*, Field*, bool) const (sql_type.cc:4323)

==1788135==    by 0xE093CC: Item::save_in_field(Field*, bool) (item.cc:6711)

==1788135==    by 0x9A43FD: Item_result_field::save_in_result_field(bool) (item.h:3406)

==1788135==    by 0xAD627C: copy_funcs(Item**, THD const*) (sql_select.cc:26168)

==1788135==    by 0xACCDA0: end_update(JOIN*, st_join_table*, bool) (sql_select.cc:22562)

==1788135==    by 0xADFC6F: AGGR_OP::put_record(bool) (sql_select.cc:29317)

==1788135==    by 0xAE7B04: AGGR_OP::put_record() (sql_select.h:1056)

==1788135==    by 0xAC841B: sub_select_postjoin_aggr(JOIN*, st_join_table*, bool) (sql_select.cc:20710)

==1788135==    by 0xAC9101: evaluate_join_record(JOIN*, st_join_table*, int) (sql_select.cc:21217)

==1788135==    by 0xAC89B8: sub_select(JOIN*, st_join_table*, bool) (sql_select.cc:20994)

==1788135==    by 0xAC7DD9: do_select(JOIN*, Procedure*) (sql_select.cc:20541)

double free or corruption (out)

210526 13:53:09 [ERROR] mysqld got signal 6 ;

This could be because you hit a bug. It is also possible that this binary

or one of the libraries it was linked against is corrupt, improperly built,

or misconfigured. This error can also be caused by malfunctioning hardware.

To report this bug, see https://mariadb.com/kb/en/reporting-bugs

We will try our best to scrape up some info that will hopefully help

diagnose the problem, but since we have already crashed, 

something is definitely wrong and this may fail.

Server version: 10.6.2-MariaDB-log

key_buffer_size=1048576

read_buffer_size=131072

max_used_connections=1

max_threads=153

thread_count=1

It is possible that mysqld could use up to 

key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 63732 K  bytes of memory

Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x7f1c24000c58

Attempting backtrace. You can use the following information to find out

where mysqld died. If you see no messages after this, something went

terribly wrong...

stack_bottom = 0x7f1c4036fd98 thread_stack 0x49000

commit 36cdd5c3cdb06d8538f64c0b312ffe4672a92e75

Author: Monty

Date:   Wed Sep 16 11:23:50 2020 +0300

    Optimize usage of c_ptr(), c_ptr_quick() and String::alloc()