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Re: [libvirt] PATCH: 4/5: Support daemonizing child & env variables



On Tue, Aug 19, 2008 at 11:10:49PM +0200, Jim Meyering wrote:
> "Daniel P. Berrange" <berrange redhat com> wrote:
> > On Tue, Aug 19, 2008 at 10:51:29PM +0200, Jim Meyering wrote:
> >> "Daniel P. Berrange" <berrange redhat com> wrote:
> >> > Some of the existing usage of fork/exec in libvirt is done such that the
> >> > child process is daemonized. In particular the libvirt_proxy and the
> >> > auto-spawned  libvirtd for qemu:///session. Since we want to switch these
> >> > to use virExec, we need to suport a daemon mode.
> >> >
> >> > This patch removes the two alternate virExec and virExecNonBlock functions
> >> > and renames the internal __virExec to virExec. It then gains a 'flags'
> >> > parameter which can be used to specify non-blocking mode, or daemon mode.
> >> >
> >> > We also add the ability to pass in a list of environment variables which
> >> > get passed on to execve(). We also now explicitly close all file handles.
> >> > Although libvirt code is careful to set O_CLOSEXEC on all its file handles,
> >> > in multi-threaded apps there is a race condition between opening a FD and
> >> > setting O_CLOSEXEC. Furthermore, we can't guarentee that all applications
> >> > using libvirt are careful to set O_CLOSEXEC. Leaking FDs to a child is a
> >> > potential security risk and often causes SELinux AVCs to be raised. Thus
> >> > explicitely  closing all FDs is a important safety net.
> >>
> >> How about closing those FDs in the child instead, right after the fork?
> >> Then, if a virExec caller has an open socket or file descriptor,
> >> it won't be closed behind its back.
> >
> > This is being done after a fork(). The diff context in this patch is
> > a little misleading. The fork() shown here is the 2nd optional fork() done
> > in daemon mode. The first fork() is higher up before we close the FDs.
> 
> I should have known.  Next time I'll review with the full context.
> ACK, then.

Ok, committed now.

Daniel
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