Description:
Oracle's tool called Discover detects UMR (Uninitialized Memory Read)
in mysqld server when executing '1st' test case located inside
MySQL 5.7.10. This UMR was produced on Sparc Solaris 11.3 T7 system,
but it's not platform specific, and can occur on any other platform.
Error message and call stack reported by Discover looks like this:
======================================
(UMR): accessing uninitialized data ... (4 bytes) on the heap:
ull2dec() + 0x2b4 <decimal.c : 1071>
1071:=> sanity(to);
longlong2decimal() + 0x230 <decimal.c : 1108>
1108:=> return ull2dec(from, to);
int2my_decimal(unsigned int, long long, char, my_decimal*)... <my_decimal.h : 438>
438:=> return d->check_result(mask, (unsigned_flag ?
Item_decimal::Item_decimal(long long, bool) + 0x5ec <item.cc : 3350>
3350:=> int2my_decimal(E_DEC_FATAL_ERROR, val, unsig, &decimal_value);
create_schema_table(THD*, TABLE_LIST*) + 0x1658 <sql_show.cc : 7568>
7568:=> if (!(item= new Item_decimal((longlong) fields_info->value, false)))
mysql_schema_table(THD*, LEX*, TABLE_LIST*) + 0x300 <sql_show.cc : 7843>
7843:=> if (!(table= table_list->schema_table->create_table(thd, table_list)))
open_and_process_table(THD*, LEX*, TABLE_LIST*, ... <sql_base.cc : 4943>
4943:=> !check_and_update_table_version(thd, tables, tables->table->s))
open_tables(THD*, TABLE_LIST**, unsigned int*, ... <sql_base.cc : 5663>
5663:=> has_prelocking_list, &ot_ctx);
Was allocated at (7968 bytes) [t@25]:
my_raw_malloc() + 0x2a4 <my_malloc.c : 191>
191:=> point= malloc(size);
my_malloc() + 0x1a4 <my_malloc.c : 54>
54:=> mh= (my_memory_header*) my_raw_malloc(raw_size, flags);
alloc_root() + 0xea0 <my_alloc.c : 280>
280:=> get_size,MYF(MY_WME | ME_FATALERROR))))
Query_arena::mem_calloc(unsigned long) + 0x1bc <sql_class.h : 747>
747:=> if ((ptr=alloc_root(mem_root,size)))
st_select_lex::add_table_to_list(THD*, Table_ident*,... <sql_parse.cc : 5819>
5819:=> if (!(ptr = (TABLE_LIST *) thd->mem_calloc(sizeof(TABLE_LIST))))
make_table_list(THD*, st_select_lex*, ... <sql_show.cc : 3154>
3154:=> if (!sel->add_table_to_list(thd,table_ident,0,0,TL_READ,MDL_SHARED_READ))
fill_schema_table_by_open(THD*, st_mem_root*, ... <sql_show.cc : 3831>
3831:=> if (make_table_list(thd, lex->select_lex, db_name_lex_cstr,
get_all_tables(THD*, TABLE_LIST*, Item*) + 0x4600 <sql_show.cc : 4640>
4640:=> if (fill_schema_table_by_open(thd, &tmp_mem_root, FALSE,
======================================
How to repeat:
1. If you have access to Discover tool, and latest Sun Stidio C/C++ compilers
you need to build MySQL-5.7.10 sources in debug mode on Solaris Sparc,
then launch discover binary with input argument as mysqld binary,
and when completed to take a look inside mysql.html file which should
contain call stack shown in description above.
2. If you do not have access to Discover, you need to debug MySQL server
with '1st' test case, and to see that 'low' argument located
inside strings/decimal.c line ~1071
sanity(to);
is indeed uninitialized before that point.
Below is 35 lines independent executable t.cc test case which accurately
simulates original issue. For it Discover produces exactly the same UMR
message as for original mysqld server.
t.cc
===================================
typedef struct st_decimal_t {
int len;
int *buf;
} decimal_t;
class my_decimal
: public decimal_t
{
int buffer[9];
public:
my_decimal & operator=(const my_decimal &rhs) {
decimal_t::operator=(rhs);
for (unsigned i= 0; i < 9; i++) {
buffer[i]= rhs.buffer[i];
}
buf= buffer;
return *this;
}
void init() {
len= 9;
buf= buffer;
}
my_decimal() {
init();
}
};
inline void my_decimal2decimal(const my_decimal *from, my_decimal *to) {
*to=*from;
}
int main() {
my_decimal md1,md2, *pmd2=&md2;
const my_decimal *pmd1=&md1;
my_decimal2decimal(pmd1,pmd2);
return 0;
}
===================================
Suggested fix:
Somehow initialize 'to' argument before passing its value into sanity(to);
Description: Oracle's tool called Discover detects UMR (Uninitialized Memory Read) in mysqld server when executing '1st' test case located inside MySQL 5.7.10. This UMR was produced on Sparc Solaris 11.3 T7 system, but it's not platform specific, and can occur on any other platform. Error message and call stack reported by Discover looks like this: ====================================== (UMR): accessing uninitialized data ... (4 bytes) on the heap: ull2dec() + 0x2b4 <decimal.c : 1071> 1071:=> sanity(to); longlong2decimal() + 0x230 <decimal.c : 1108> 1108:=> return ull2dec(from, to); int2my_decimal(unsigned int, long long, char, my_decimal*)... <my_decimal.h : 438> 438:=> return d->check_result(mask, (unsigned_flag ? Item_decimal::Item_decimal(long long, bool) + 0x5ec <item.cc : 3350> 3350:=> int2my_decimal(E_DEC_FATAL_ERROR, val, unsig, &decimal_value); create_schema_table(THD*, TABLE_LIST*) + 0x1658 <sql_show.cc : 7568> 7568:=> if (!(item= new Item_decimal((longlong) fields_info->value, false))) mysql_schema_table(THD*, LEX*, TABLE_LIST*) + 0x300 <sql_show.cc : 7843> 7843:=> if (!(table= table_list->schema_table->create_table(thd, table_list))) open_and_process_table(THD*, LEX*, TABLE_LIST*, ... <sql_base.cc : 4943> 4943:=> !check_and_update_table_version(thd, tables, tables->table->s)) open_tables(THD*, TABLE_LIST**, unsigned int*, ... <sql_base.cc : 5663> 5663:=> has_prelocking_list, &ot_ctx); Was allocated at (7968 bytes) [t@25]: my_raw_malloc() + 0x2a4 <my_malloc.c : 191> 191:=> point= malloc(size); my_malloc() + 0x1a4 <my_malloc.c : 54> 54:=> mh= (my_memory_header*) my_raw_malloc(raw_size, flags); alloc_root() + 0xea0 <my_alloc.c : 280> 280:=> get_size,MYF(MY_WME | ME_FATALERROR)))) Query_arena::mem_calloc(unsigned long) + 0x1bc <sql_class.h : 747> 747:=> if ((ptr=alloc_root(mem_root,size))) st_select_lex::add_table_to_list(THD*, Table_ident*,... <sql_parse.cc : 5819> 5819:=> if (!(ptr = (TABLE_LIST *) thd->mem_calloc(sizeof(TABLE_LIST)))) make_table_list(THD*, st_select_lex*, ... <sql_show.cc : 3154> 3154:=> if (!sel->add_table_to_list(thd,table_ident,0,0,TL_READ,MDL_SHARED_READ)) fill_schema_table_by_open(THD*, st_mem_root*, ... <sql_show.cc : 3831> 3831:=> if (make_table_list(thd, lex->select_lex, db_name_lex_cstr, get_all_tables(THD*, TABLE_LIST*, Item*) + 0x4600 <sql_show.cc : 4640> 4640:=> if (fill_schema_table_by_open(thd, &tmp_mem_root, FALSE, ====================================== How to repeat: 1. If you have access to Discover tool, and latest Sun Stidio C/C++ compilers you need to build MySQL-5.7.10 sources in debug mode on Solaris Sparc, then launch discover binary with input argument as mysqld binary, and when completed to take a look inside mysql.html file which should contain call stack shown in description above. 2. If you do not have access to Discover, you need to debug MySQL server with '1st' test case, and to see that 'low' argument located inside strings/decimal.c line ~1071 sanity(to); is indeed uninitialized before that point. Below is 35 lines independent executable t.cc test case which accurately simulates original issue. For it Discover produces exactly the same UMR message as for original mysqld server. t.cc =================================== typedef struct st_decimal_t { int len; int *buf; } decimal_t; class my_decimal : public decimal_t { int buffer[9]; public: my_decimal & operator=(const my_decimal &rhs) { decimal_t::operator=(rhs); for (unsigned i= 0; i < 9; i++) { buffer[i]= rhs.buffer[i]; } buf= buffer; return *this; } void init() { len= 9; buf= buffer; } my_decimal() { init(); } }; inline void my_decimal2decimal(const my_decimal *from, my_decimal *to) { *to=*from; } int main() { my_decimal md1,md2, *pmd2=&md2; const my_decimal *pmd1=&md1; my_decimal2decimal(pmd1,pmd2); return 0; } =================================== Suggested fix: Somehow initialize 'to' argument before passing its value into sanity(to);