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Re: [libvirt] [PATCH] Close logfile fd after spawning qemu



On Thu, Sep 10, 2009 at 10:15:58AM +0100, Mark McLoughlin wrote:
> On Thu, 2009-09-10 at 11:04 +0200, Daniel Veillard wrote:
> > On Thu, Sep 10, 2009 at 02:13:56PM +0900, Ryota Ozaki wrote:
> > > Hi,
> > > 
> > > This patch closes logfile fd after spawing qemu in qemudStartVMDaemon.
> > > The fd seems to be closed in the error path, but not in the normal path.
> > > The fd is passed to virExecDaemonize though, but looks not being closed
> > > inside it. Eventually, the fd is never closed during libvirtd lifetime.
> > > 
> > > Thanks,
> > >   ozaki-r
> > > 
> > > >From b3d3e0f24c5df5c7677e539bbc2598f2d7fbc3b8 Mon Sep 17 00:00:00 2001
> > > From: Ryota Ozaki <ozaki ryota gmail com>
> > > Date: Thu, 10 Sep 2009 12:53:56 +0900
> > > Subject: [PATCH] Close logfile fd after spawning qemu
> > > 
> > > ---
> > >  src/qemu_driver.c |    1 +
> > >  1 files changed, 1 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/src/qemu_driver.c b/src/qemu_driver.c
> > > index 8f16e72..f2182c4 100644
> > > --- a/src/qemu_driver.c
> > > +++ b/src/qemu_driver.c
> > > @@ -2187,6 +2187,7 @@ static int qemudStartVMDaemon(virConnectPtr conn,
> > >                             VIR_EXEC_NONBLOCK | VIR_EXEC_CLEAR_CAPS,
> > >                             qemudSecurityHook, &hookData,
> > >                             pidfile);
> > > +    close(logfile);
> > >      VIR_FREE(pidfile);
> > > 
> > >      /* wait for qemu process to to show up */
> > 
> >   Hum, it's not quite simple.
> 
> Indeed. I only had a quick look and wasn't sure. We at least need to set
> logfile to -1 after closing it to avoid trying to close it again further
> down.

  Okay, the fd is passed by address to virExecDaemonize, since it was
properly initialized it should not be overwritten by __virExec, but as a
safety I think this should be checked for -1 before close. The fd is not
written anywhere, so we are pretty much sure it's a lost fd at this
point and there is no way the application could use it beyond the
function return. I'm just changing the patch slightly to 

diff --git a/src/qemu_driver.c b/src/qemu_driver.c
index 5c2a8ec..d778a89 100644
--- a/src/qemu_driver.c
+++ b/src/qemu_driver.c
@@ -2239,6 +2239,9 @@ static int qemudStartVMDaemon(virConnectPtr conn,
         /* No need for 'goto cleanup' now since qemudShutdownVMDaemon does enou
     }
 
+    if (logfile != -1)
+        close(logfile);
+
     return ret;
 
 cleanup:


 i.e. check for -1 and close only at the non-cleanup return point.
I just commited this.

  thanks !

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel veillard com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/


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