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 (1 byte) on the heap:
mysql_checksum_table(THD*, TABLE_LIST*, st_ha_check_opt*) + 0x2f6c <sql_table.cc : 10362>
10362:=> t->record[0][t->s->null_bytes-1] |= null_mask;
mysql_execute_command(THD*, bool) + 0xe2f0 <sql_parse.cc : 3471>
3471:=> res = mysql_checksum_table(thd, first_table, &lex->check_opt);
sp_instr_stmt::exec_core(THD*, unsigned int*) + 0x748 <sp_instr.cc : 948>
948:=> bool rc= mysql_execute_command(thd);
sp_lex_instr::reset_lex_and_exec_core(THD*, unsigned int*, bool) + 0x2a9c <sp_instr.cc : 411>
411:=> error= exec_core(thd, nextp);
sp_lex_instr::validate_lex_and_execute_core(THD*, unsigned int*, bool) + 0xc80 <sp_instr.cc : 676>
676:=> bool rc= reset_lex_and_exec_core(thd, nextp, open_tables);
sp_instr_stmt::execute(THD*, unsigned int*) + 0x1268 <sp_instr.cc : 859>
859:=> rc= validate_lex_and_execute_core(thd, nextp, false);
sp_head::execute(THD*, bool) + 0x404c <sp_head.cc : 789>
789:=> err_status= i->execute(thd, &ip);
sp_head::execute_procedure(THD*, List<Item>*) + 0x3924 <sp_head.cc : 1522>
1522:=> err_status= execute(thd, TRUE);
Was allocated at (1024 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))))
Sql_alloc::operator new(unsigned long, st_mem_root*) + 0x110 <sql_alloc.h : 39>
39:=> { return alloc_root(mem_root, size); }
innobase_create_handler(handlerton*, TABLE_SHARE*, st_mem_root*) + 0x660 <ha_innodb.cc : 1327>
1327:=> return(new (mem_root) ha_innobase(hton, table));
get_new_handler(TABLE_SHARE*, st_mem_root*, handlerton*) + 0x4a0 <handler.cc : 652>
652:=> if ((file= db_type->create(db_type, share, alloc)))
open_table_from_share(THD*, TABLE_SHARE*, ... <table.cc : 3050>
3050:=> share->db_type())))
open_table(THD*, TABLE_LIST*, Open_table_context*) + 0x5dec <sql_base.cc : 3473>
3473:=> thd->open_options, table, FALSE);
======================================
How to repeat:
1. If you have access to Discover tool, and latest Sun Studio 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 t->record[0][t->s->null_bytes-1] operand located
inside sql/sql_table.cc mysql_check_table() line ~10362
t->record[0][t->s->null_bytes-1] |= null_mask;
is indeed uninitialized before that point.
Below is 33 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
===================================
#include <stdlib.h>
typedef unsigned char uchar;
typedef unsigned int uint;
struct TABLE_SHARE {
TABLE_SHARE() {}
uint null_bytes;
};
struct TABLE {
TABLE() {}
TABLE_SHARE *s;
uchar *record[2];
};
void open_table_from_share(TABLE_SHARE *share,TABLE *outparam) {
uint records=2;
uchar *record;
outparam->s=share;
record=(uchar*)malloc(496);
outparam->record[0]=record;
}
void mysql_checksum_table(TABLE *t) {
uchar null_mask=254;
t->record[0][t->s->null_bytes-1] |= null_mask;
}
int main () {
TABLE_SHARE *pts;
TABLE *pt;
pt=(TABLE*)malloc(sizeof(TABLE));
pts=(TABLE_SHARE*)malloc(sizeof(TABLE_SHARE));
pts->null_bytes=1;
open_table_from_share(pts,pt);
mysql_checksum_table(pt);
return 0;
}
===================================
Suggested fix:
Somehow initialize t->record[0][t->s->null_bytes-1] operand before its read in:
t->record[0][t->s->null_bytes-1] |= null_mask;
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 (1 byte) on the heap: mysql_checksum_table(THD*, TABLE_LIST*, st_ha_check_opt*) + 0x2f6c <sql_table.cc : 10362> 10362:=> t->record[0][t->s->null_bytes-1] |= null_mask; mysql_execute_command(THD*, bool) + 0xe2f0 <sql_parse.cc : 3471> 3471:=> res = mysql_checksum_table(thd, first_table, &lex->check_opt); sp_instr_stmt::exec_core(THD*, unsigned int*) + 0x748 <sp_instr.cc : 948> 948:=> bool rc= mysql_execute_command(thd); sp_lex_instr::reset_lex_and_exec_core(THD*, unsigned int*, bool) + 0x2a9c <sp_instr.cc : 411> 411:=> error= exec_core(thd, nextp); sp_lex_instr::validate_lex_and_execute_core(THD*, unsigned int*, bool) + 0xc80 <sp_instr.cc : 676> 676:=> bool rc= reset_lex_and_exec_core(thd, nextp, open_tables); sp_instr_stmt::execute(THD*, unsigned int*) + 0x1268 <sp_instr.cc : 859> 859:=> rc= validate_lex_and_execute_core(thd, nextp, false); sp_head::execute(THD*, bool) + 0x404c <sp_head.cc : 789> 789:=> err_status= i->execute(thd, &ip); sp_head::execute_procedure(THD*, List<Item>*) + 0x3924 <sp_head.cc : 1522> 1522:=> err_status= execute(thd, TRUE); Was allocated at (1024 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)))) Sql_alloc::operator new(unsigned long, st_mem_root*) + 0x110 <sql_alloc.h : 39> 39:=> { return alloc_root(mem_root, size); } innobase_create_handler(handlerton*, TABLE_SHARE*, st_mem_root*) + 0x660 <ha_innodb.cc : 1327> 1327:=> return(new (mem_root) ha_innobase(hton, table)); get_new_handler(TABLE_SHARE*, st_mem_root*, handlerton*) + 0x4a0 <handler.cc : 652> 652:=> if ((file= db_type->create(db_type, share, alloc))) open_table_from_share(THD*, TABLE_SHARE*, ... <table.cc : 3050> 3050:=> share->db_type()))) open_table(THD*, TABLE_LIST*, Open_table_context*) + 0x5dec <sql_base.cc : 3473> 3473:=> thd->open_options, table, FALSE); ====================================== How to repeat: 1. If you have access to Discover tool, and latest Sun Studio 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 t->record[0][t->s->null_bytes-1] operand located inside sql/sql_table.cc mysql_check_table() line ~10362 t->record[0][t->s->null_bytes-1] |= null_mask; is indeed uninitialized before that point. Below is 33 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 =================================== #include <stdlib.h> typedef unsigned char uchar; typedef unsigned int uint; struct TABLE_SHARE { TABLE_SHARE() {} uint null_bytes; }; struct TABLE { TABLE() {} TABLE_SHARE *s; uchar *record[2]; }; void open_table_from_share(TABLE_SHARE *share,TABLE *outparam) { uint records=2; uchar *record; outparam->s=share; record=(uchar*)malloc(496); outparam->record[0]=record; } void mysql_checksum_table(TABLE *t) { uchar null_mask=254; t->record[0][t->s->null_bytes-1] |= null_mask; } int main () { TABLE_SHARE *pts; TABLE *pt; pt=(TABLE*)malloc(sizeof(TABLE)); pts=(TABLE_SHARE*)malloc(sizeof(TABLE_SHARE)); pts->null_bytes=1; open_table_from_share(pts,pt); mysql_checksum_table(pt); return 0; } =================================== Suggested fix: Somehow initialize t->record[0][t->s->null_bytes-1] operand before its read in: t->record[0][t->s->null_bytes-1] |= null_mask;