Wrong Handling of pid files (example: fcgiwrap) forces single user mode. Am I correct?

[Jim Ohlstein]

On Fri, 2017-06-02 at 03:02 -0700, BBlister wrote:
> Hello,
> 
> One of my servers (running 10.3-RELEASE-p18) faced a serious problem
> out of
> the blue. It booted normally multiuser, but after a while it switched
> to
> single user only, terminating all networking sevices (like SSHD).
> This was
> done automatically. I was able to access it only via remote serial
> port. 
> 
> I found out the culprit:
> In my setup I have all the services disable in /etc/rc.conf to speed
> up the
> booting process, and when the system is up, then a crontab entry for
> every
> service like "@reboot (delay 120;/usr/local/etc/rc.d/fcgiwrap
> onerestart )"  
> issues the command to initiate the specific service.
> 
> All the services start from @reboot entries at crontab. But I
> discovered
> that the init script for fcgiwrap  (and possible other ports that use
> similar rc files) has a serious bug, when the command 'onerestart' is
> applied.
> 
> If the command line parameter onerestart is used, then this script
> first
> tries to terminate the process and then restarts it. The problem is
> that in
> the termination function has this code:
> 
> ...
> fcgiwrap_stop() {
>         fcgiwrap_pgrp=$(/bin/ps -o ppid= $(cat ${pidfile}))
>  ...
> 
> The problem is that if the ${pidfile} does not exist then this
> command
> returns the PID 1 among other PIDS, like this:
> 
> /bin/ps -o ppid= $(cat /var/run/fcgiwrap/fcgiwrap.pid)
> 
> cat: /var/run/fcgiwrap/fcgiwrap.pid: No such file or directory
> 72303
>     1
> 71730
> 72092
>     1
>     1
>     1
>  
> and then using a command  kill -TERM -- -${fcgiwrap_pgrp}
> terminates all these pids.
> 
> But, PID 1 is the /sbin/init  and according to init(8) 
> ...init will signal the original (PID 1) init as follows:
> ....
> 1            SIGTERM    Go to single-user mode
> 
> 
> So the fastcgiwrap sends SIGTERM to /sbin/init and then systems
> reverts to
> single user mode.
> 
> 
> The fix is to first check the existance of the file, like
> 
> if [ -f  ${pidfile} ] ; then ....
> 
> 
> and not just 'cat' and 'kill' whatever it returns.

Does the same thing happen if you use 'onestart' instead of 'one
restart'?

> 
> 
> Took me a while to debug it and found the solution, and I post it
> here to
> help future admins...
> 

-- 
Jim Ohlstein
Professional Mailman Hosting
https://mailman-hosting.com/