MySQL Bugs: #9175: seg fault on 'mysqldump --single-transaction --tab mysql nonexistent'

Bug #9175	seg fault on 'mysqldump --single-transaction --tab mysql nonexistent'
Submitted:	14 Mar 2005 23:02	Modified:	26 Apr 2005 2:17
Reporter:	Tim Smith
Status:	Closed
Category:	Client	Severity:	S3 (Non-critical)
Version:	4.1.11	OS:	Any (any)
Assigned to:	Reggie Burnett	Target Version:

Description:
15:00 ~/m/41/m$ mysqldump --single-transaction --tab=/tmp/foo/ mysql nonexistent
zsh: segmentation fault (core dumped)  mysqldump --single-transaction --tab=/tmp/foo/
mysql nonexistent

However, it works to pass an existing table:

14:59 ~/m/41/m$ mysqldump --single-transaction --tab=/tmp/foo/ mysql user
15:00 ~/m/41/m$

I tested on FreeBSD 5.4, recent 4.1.11-pre code from BK.

How to repeat:

mysqldump --single-transaction --tab=/tmp/foo/ mysql nonexistent

For a simpler testcase:
(gdb) r --lock-tables=0 mysql non
Starting program: /home/mysql_src/mysql-4.1-clean/client/.libs/lt-mysqldump
--lock-tables=0 mysql non
-- MySQL dump 10.9
--
-- Host: localhost    Database: mysql
-- ------------------------------------------------------
-- Server version       4.0.23-debug-log
/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;

Program received signal SIGSEGV, Segmentation fault.
0x0804e246 in get_actual_table_name (old_table_name=0xbffff300 "non",
new_table_name=0xbfffeed0 "\f\177", buf_size=64)
    at mysqldump.c:2120
2120      strmake(new_table_name, row[0], buf_size-1);
"row" is 0 (because the SHOW TABLES query returns nothing).

If lock_tables is set, mysqldump detects the non-existency during LOCK TABLES.

mysqldump 4.0 does not have the problem.

Reggie, this is your get_actual_table_name(): you may want to detect when the SHOW TABLES
LIKE returns no rows (inexistent table) and return info to the caller (so that caller
skips dumping the table), instead of dereferencing "row" which is a null pointer. Thanks!!

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/internals/23416

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/internals/23531

Fixed in 4.1.11 and 5.0.4.

err, correcton.  I think this bug will appear in 5.0.4 and 4.1.12

Noted in 4.1.12, 5.0.4 changelogs.