event_handler pipe fd inheritation

[Bastian Friedrich]

Hi,

we are using a mechanism in our event_handlers that shall try to restart 
broken local services; eventually, normal init scripts (/etc/init.d/...) are 
started, which in turn start arbitrary daemons (say, mysql).

nagios creates a pipe to its event_handlers (and possibly other executables) 
in base/util.c for parent/child communication. The file descriptor to this 
pipe is (currently) not given the FD_CLOEXEC. This results in this fd being 
inherited by the event_handler (started by "popen()"), and, in our case, by 
the daemon (say, mysql). (The pipe is, e.g., visible in /proc/<whatever>/fd). 
As our daemons do not tend to close arbitrary fd's, this fd is never closed 
from the event_handler. As nagios waits for the file to be closed to continue 
its work, this results in a "denial of service" for the time that the daemon 
runs.

The pipe fd should be set the FD_CLOEXEC flag; it is then not inherited by the 
event_handler.

Patch attached.

Best regards
   Bastian

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