Windows

Fixed in development branch svn://svn.zabbix.com/branches/dev/ZBX-6584

The problem happens when a log file was removed between agent calling stat() and open() on a log file. When this happens open() results in an error and next call to close() results in crash. Steps to reproduce:

• let zabbix agent call stat() on the log file
• sleep
• remove the log file
• let zabbix agent call open() on the log file (open() fails which results in file descriptor set to -1)
• let zabbix agent call close(-1), it crashes

Before the fix the check for close was in place but it just checked for file descriptor != 0, it did not handle situation when it would be -1. The fix is to call close() only when file descriptor is greater than 0.

Successfully tested.

The problem does not happen with log items, only logrt.

Released in:
pre-1.8.17rc1 r35519
pre-2.0.7 r35520
pre-2.1.0 r35521

Reopen to add labels - could be useful for future.
Closed again.

So, a real world case could be as follows:

• foo.log file is monitored by zabbix agent
• also foo.log file is being rotated by logrotater
• zabbix agent checks if foo.log exists, success
• now at this point logrotater decides the log is too big and compresses it, moving the contents to a new file foo.log.gz.1
• foo.log disappears
• zabbix agent continues it's routines with foo.log, it's time to read the data from it
• crash

Technically the problem is incorrect error handling of open() system call.

Another point, the crash is possible only on a Windows platform.