| Bug #71559 | Max_data_length has integer overflow on some memory tables | ||
|---|---|---|---|
| Submitted: | 2 Feb 2014 12:29 | ||
| Reporter: | Shane Bester (Platinum Quality Contributor) | Email Updates: | |
| Status: | Verified | Impact on me: | |
| Category: | MySQL Server: Memory storage engine | Severity: | S3 (Non-critical) |
| Version: | 5.0.96 | OS: | Microsoft Windows |
| Assigned to: | CPU Architecture: | Any | |
[2 Feb 2014 13:01]
Shane Bester
This is the assembly: stats.max_data_file_length= hp_info.max_records * hp_info.reclength; 000000014020DA8E mov eax,dword ptr [rsp+30h] 000000014020DA92 imul eax,dword ptr [rsp+48h] 000000014020DA97 mov eax,eax 000000014020DA99 mov rcx,qword ptr [rsp+90h] 000000014020DAA1 mov qword ptr [rcx+48h],rax rsp+30h has value 0x30000000 (decimal 805306368) rsp+48h has value 0x10 (decimal 16) After imul, the flags are showing overflow: OV = 1 UP = 0 EI = 1 PL = 0 ZR = 0 AC = 0 PE = 1 CY = 1
[2 Feb 2014 13:09]
Shane Bester
I fixed it by casting things to ulonglong:
=== modified file 'storage/heap/ha_heap.cc'
--- storage/heap/ha_heap.cc 2014-01-06 06:02:04 +0000
+++ storage/heap/ha_heap.cc 2014-02-02 13:02:38 +0000
@@ -406,7 +406,7 @@
stats.mean_rec_length= hp_info.reclength;
stats.data_file_length= hp_info.data_length;
stats.index_file_length= hp_info.index_length;
- stats.max_data_file_length= hp_info.max_records * hp_info.reclength;
+ stats.max_data_file_length= (ulonglong)hp_info.max_records * (ulonglong)hp_info.reclength;
stats.delete_length= hp_info.deleted * hp_info.reclength;
stats.create_time= (ulong) hp_info.create_time;
if (flag & HA_STATUS_AUTO)
So now the result is shown correctly:
mysql> show table status like 't1'\G
*************************** 1. row ***************************
Name: t1
Engine: MEMORY
Version: 10
Row_format: Fixed
Rows: 2
Avg_row_length: 16
Data_length: 126984
Max_data_length: 12884901888 <--------
Index_length: 0
Data_free: 0
Auto_increment: NULL
Create_time: 2014-02-02 15:05:50
Update_time: NULL
Check_time: NULL
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (41.71 sec)
[2 Feb 2014 13:11]
Shane Bester
I'm unsure why the compiler (VS2010) cannot handle this by itself.
[2 Feb 2014 13:27]
Shane Bester
The assembly of the working patch is now showing that full RAX is used. stats.max_data_file_length= (ulonglong)hp_info.max_records * (ulonglong)hp_info.reclength; 000000014039DA8E mov eax,dword ptr [rsp+30h] 000000014039DA92 mov ecx,dword ptr [rsp+48h] 000000014039DA96 imul rax,rcx 000000014039DA9A mov rcx,qword ptr [rsp+90h] 000000014039DAA2 mov qword ptr [rcx+48h],rax
Description: Tested on 5.0, 5.1, 5.5, 5.6, 5.7 on Windows x64. Linux x64 was okay. At least on windows 64-bit, the Max_data_length is wrong: mysql> show table status like 't1'\G *************************** 1. row *************************** Name: t1 Engine: MEMORY Version: 10 Row_format: Fixed Rows: 2 Avg_row_length: 16 Data_length: 126984 Max_data_length: 0 <----------- Index_length: 0 Data_free: 0 Auto_increment: NULL Create_time: 2014-02-02 14:26:09 Update_time: NULL Check_time: NULL Collation: latin1_swedish_ci Checksum: NULL Create_options: Comment: 1 row in set (0.00 sec) How to repeat: set tmp_table_size=1024*1024*1024*18; set max_heap_table_size=1024*1024*1024*18; drop table if exists `t1`; create table `t1` (`a` tinyint,`b` tinyint,`c` double,`d` timestamp,`e` tinyint) engine=memory ; insert into `t1` values (),(); show table status like 't1'\G