[syslog-ng] race condition in destination driver deinit?

[Michael Hocke]

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Me again....

Hi guys,

I've been running 3.3.3 on Solaris 10 x86 for quite a bit now. I've got two boxes, both running the same OS release and the same release of syslog-ng. One of them (box A) has a destination configured that doesn't really exist so I've been getting 

Mar 13 14:46:15 flowmon-sys syslog-ng[20118]: I/O error occurred while writing; fd='24', error='Connection refused (146)'

which is perfectly fine and I just ignored it. The other Solaris box (box B) does not have this destination configured. It now happens that after a random number of HUP signals syslog-ng on box A crashes with a segmentation fault and the following backtrace:

(gdb) bt
#0  0xfef2a7a8 in log_dest_driver_release_queue_method (self=0x80d2958, 
    q=0x83e58955, user_data=0x0) at driver.c:80
#1  0xfef2aa5c in log_dest_driver_deinit_method (s=0x80d2958) at driver.c:80
#2  0xfe914a14 in afsocket_dd_deinit (s=0x80d2958) at afsocket.c:109
#3  0xfef29cd6 in log_dest_group_deinit (s=0x8074198) at dgroup.c:59
#4  0xfef24a21 in log_center_deinit (self=0x8090cc0) at center.c:67
#5  0xfef25493 in cfg_deinit (cfg=0x80d2848) at cfg.c:90
#6  0xfef406b2 in main_loop_reload_config_apply () at mainloop.c:364
#7  0xfef40a42 in main_loop_io_worker_sync_call (func=<value optimized out>)
    at mainloop.c:364
#8  0x08047900 in ?? ()

I was able to reproduce this over and over again. Sometimes it happens after 11 HUPs, sometimes after 35, but it eventually does crash. Since the only difference between box A and box B is the one additional destination I suspect that this is the cause for this segfault. Maybe the HUP signal came at a time when syslog-ng was trying to send something to the non-existing destination?

I'll try to collect some more data. If anybody could give me some direction on where exactly I should look into, I'll be happy to do that.

- - Michael


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