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 in "stack" ... (8 bytes) on the stack:
my_qsort() + 0xac8 <mf_qsort.c : 124>
124:=> POP(low, high);
my_dir() + 0xbb4 <my_lib.c : 160>
160:=> sizeof(FILEINFO), (qsort_cmp) comp_names);
find_files(THD*, ... <sql_show.cc : 632>
632:=> if (!(dirp = my_dir(path,MYF(dir ? MY_WANT_STAT : 0))))
make_db_list(THD*, ... <sql_show.cc : 3559>
3559:=> mysql_data_home, NullS, 1, tmp_mem_root) != FIND_FILES_OK);
fill_schema_schemata(THD*, TABLE_LIST*, Item*) + 0x620 <sql_show.cc : 4724>
4724:=> if (make_db_list(thd, &db_names, &lookup_field_vals,
do_fill_table(THD*, TABLE_LIST*, QEP_TAB*) + 0x4a4 <sql_show.cc : 8029>
8029:=> bool res= table_list->schema_table->fill_table(
get_schema_tables_result(JOIN*, enum_schema_table_state) + 0x1f04 <sql_show.cc : 8132>
8132:=> if (do_fill_table(thd, table_list, tab))
JOIN::prepare_result() + 0xae0 <sql_select.cc : 909>
909:=> get_schema_tables_result(this, PROCESSED_BY_JOIN_EXEC))
======================================
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 my_qsort.c ,line 124:
POP(low, high);
is indeed uninitialized before that point.
Below is 36 lines independent executable t.c test case which accurately
simulates original issue. For it Discover produces exactly the same UMR
message as for original mysqld server.
t.c
===================================
typedef struct fileinfo {
char *name;
} FILEINFO;
typedef struct st_my_dir {
struct fileinfo *dir_entry;
unsigned number_off_files;
} MY_DIR;
typedef struct st_stack {
char *low;
char *high;
} stack_node;
void my_qsort(void *base_ptr, unsigned count, unsigned size){
char *low, *high;
stack_node stack[64], *stack_ptr;
low =(char*)base_ptr;
high=low+size*(count-1);
stack_ptr=stack+1;
do {
char *low_ptr,*high_ptr;
for (low_ptr=low+size; low_ptr<=high; low_ptr+=size){
low=(--stack_ptr)->low;
high=stack_ptr->high;
}
} while (stack_ptr > stack);
}
int main() {
MY_DIR buffer,*result;
FILEINFO finfo[2];
char *p1=".", *p2="..";
result=&buffer;
result->dir_entry=finfo;
result->dir_entry[0].name=p1; result->dir_entry[1].name=p2;
result->number_off_files=2;
my_qsort((void *)result->dir_entry,result->number_off_files,sizeof(FILEINFO));
return 0;
}
===================================
Suggested fix:
Somehow initialize 'low' argument before passing its value into POP(low, high);
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 in "stack" ... (8 bytes) on the stack: my_qsort() + 0xac8 <mf_qsort.c : 124> 124:=> POP(low, high); my_dir() + 0xbb4 <my_lib.c : 160> 160:=> sizeof(FILEINFO), (qsort_cmp) comp_names); find_files(THD*, ... <sql_show.cc : 632> 632:=> if (!(dirp = my_dir(path,MYF(dir ? MY_WANT_STAT : 0)))) make_db_list(THD*, ... <sql_show.cc : 3559> 3559:=> mysql_data_home, NullS, 1, tmp_mem_root) != FIND_FILES_OK); fill_schema_schemata(THD*, TABLE_LIST*, Item*) + 0x620 <sql_show.cc : 4724> 4724:=> if (make_db_list(thd, &db_names, &lookup_field_vals, do_fill_table(THD*, TABLE_LIST*, QEP_TAB*) + 0x4a4 <sql_show.cc : 8029> 8029:=> bool res= table_list->schema_table->fill_table( get_schema_tables_result(JOIN*, enum_schema_table_state) + 0x1f04 <sql_show.cc : 8132> 8132:=> if (do_fill_table(thd, table_list, tab)) JOIN::prepare_result() + 0xae0 <sql_select.cc : 909> 909:=> get_schema_tables_result(this, PROCESSED_BY_JOIN_EXEC)) ====================================== 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 my_qsort.c ,line 124: POP(low, high); is indeed uninitialized before that point. Below is 36 lines independent executable t.c test case which accurately simulates original issue. For it Discover produces exactly the same UMR message as for original mysqld server. t.c =================================== typedef struct fileinfo { char *name; } FILEINFO; typedef struct st_my_dir { struct fileinfo *dir_entry; unsigned number_off_files; } MY_DIR; typedef struct st_stack { char *low; char *high; } stack_node; void my_qsort(void *base_ptr, unsigned count, unsigned size){ char *low, *high; stack_node stack[64], *stack_ptr; low =(char*)base_ptr; high=low+size*(count-1); stack_ptr=stack+1; do { char *low_ptr,*high_ptr; for (low_ptr=low+size; low_ptr<=high; low_ptr+=size){ low=(--stack_ptr)->low; high=stack_ptr->high; } } while (stack_ptr > stack); } int main() { MY_DIR buffer,*result; FILEINFO finfo[2]; char *p1=".", *p2=".."; result=&buffer; result->dir_entry=finfo; result->dir_entry[0].name=p1; result->dir_entry[1].name=p2; result->number_off_files=2; my_qsort((void *)result->dir_entry,result->number_off_files,sizeof(FILEINFO)); return 0; } =================================== Suggested fix: Somehow initialize 'low' argument before passing its value into POP(low, high);