Bug 811997

+++ This bug was initially created as a clone of Bug #664783 +++

radvd uses daemonize() to daemonize itself, then creates its pidfile afterwards. This means that the process that exec'ed radvd will get back control before the pidfile has been created and/or populated, which could lead to a race condition.

This creates a problem for libvirt, which attempts to run an instance of radvd and determine its pid (for later termination) by immediately reading the pidfile. The pidfile isn't yet created when libvirtd gets back control after waitpid'ing for the radvd process, so it fails to learn the pid.

Instead of using daemonize() and creating the pidfile from the child process, radvd should do the fork manually, then create the pidfile in the parent, prior to exiting.

[...]

--- Additional comment from ppisar on 2012-04-12 11:32:45 GMT ---

Upstream has fixed this issue by using libdaemon with the following patch set:

commit 1cda2ef33f505be34e690d1b7a1e5eac632819af
Author: Petr Písař <ppisar>
Date:   Wed Apr 11 13:52:24 2012 +0200

    Use pkg-config to discover libdaemon

commit 4ff814023cf62e59a6048a2cc57c62e0664d3c56
Author: Petr Písař <ppisar>
Date:   Thu Apr 5 15:24:22 2012 +0200

    Use libdaemon for daemonization
    
    The libc daemon(3) function suffers from race bewtween exiting parent
    and saving PID into a file.
    
    Using libdaemon library one can avoid this race and can simplify PID
    file manipulation.
    
    The only difference against older implementation is, the PID file will
    be inspected, created, and removed only if daemonization is requested.

--- Additional comment from ppisar on 2012-04-12 13:22:08 GMT ---

Created attachment 577068 [details]
Reproducer

Use positional arguments to select executable, timeout, and PID file location.
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All Fedoras are affected.