[libvirt] [PATCH] daemon: Fix core dumps if unix_sock_group is set

[Jiri Denemark]

> > Setting unix_sock_group to something else than default "root" in
> > /etc/libvirt/libvirtd.conf prevents system libvirtd from dumping core on
> > crash. This is because we used setgid(unix_sock_group) before binding to
> > /var/run/libvirt/libvirt-sock* and setgid() back to original group.
> > However, if a process changes its effective or filesystem group ID, it
> > will be forbidden from leaving core dumps unless fs.suid_dumpable sysctl
> > is set to something else then 0 (and it is 0 by default).
> > 
> > Changing socket's group ownership after bind works better. And we can do
> > so without introducing a race condition since we loosen access rights by
> > changing the group from root to something else.
> 
> If you use  fchown(sock->fd) then you avoid any possible race issues.

Except that it doesn't work. That was the first thing I tried but fchown()
doesn't seem to work on unix sockets. The socket will still ended up with
root:root ownership regardless on where I put fchown() -- either before bind()
to avoid race issues or after it, which wouldn't be any better than chown().

Jirka