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Re: [libvirt] PATCH: Fix permissions problem starting QEMU



On Thu, Jul 30, 2009 at 03:00:53PM +0100, Daniel P. Berrange wrote:
> 
> There is a minor bug when running QEMU non-root, and having
> capng enabled. libvirt is unable to write the PID file in
> /var/run/libvirt/qemu, since its now owned by 'qemu', but
> libvirtd has dropped all capabilties at this point. The fix
> is to delay dropping capabilities until after the PID file
> has been created. We should also be sure to kill the child
> if writing the PID file fails
[...]
> diff --git a/src/qemu_driver.c b/src/qemu_driver.c
> index 9fb8506..26897d3 100644
> --- a/src/qemu_driver.c
> +++ b/src/qemu_driver.c
> @@ -468,7 +468,7 @@ qemudStartup(int privileged) {
>              goto out_of_memory;
>  
>          if (virAsprintf(&qemu_driver->stateDir,
> -                      "%s/run/libvirt/qemu/", LOCAL_STATE_DIR) == -1)
> +                      "%s/run/libvirt/qemu", LOCAL_STATE_DIR) == -1)
>              goto out_of_memory;
>      } else {
>          uid_t uid = geteuid();

  unrelated but fine

> diff --git a/src/util.c b/src/util.c
> index ee64b28..39aae24 100644
> --- a/src/util.c
> +++ b/src/util.c
> @@ -513,12 +513,6 @@ __virExec(virConnectPtr conn,
>          if ((hook)(data) != 0)
>              _exit(1);
>  
> -    /* The hook above may need todo something privileged, so
> -     * we delay clearing capabilities until now */
> -    if ((flags & VIR_EXEC_CLEAR_CAPS) &&
> -        virClearCapabilities() < 0)
> -        _exit(1);
> -
>      /* Daemonize as late as possible, so the parent process can detect
>       * the above errors with wait* */
>      if (flags & VIR_EXEC_DAEMON) {
> @@ -543,6 +537,9 @@ __virExec(virConnectPtr conn,
>  
>          if (pid > 0) {
>              if (pidfile && virFileWritePidPath(pidfile,pid)) {
> +                kill(pid, SIGTERM);
> +                usleep(500*1000);
> +                kill(pid, SIGTERM);
>                  virReportSystemError(conn, errno,
>                                       "%s", _("could not write pidfile"));
>                  _exit(1);

  minor nitpick I would error first and then do the kill

> @@ -551,6 +548,12 @@ __virExec(virConnectPtr conn,
>          }
>      }
>  
> +    /* The steps above may need todo something privileged, so
> +     * we delay clearing capabilities until the last minute */
> +    if ((flags & VIR_EXEC_CLEAR_CAPS) &&
> +        virClearCapabilities() < 0)
> +        _exit(1);
> +
>      if (envp)
>          execve(argv[0], (char **) argv, (char**)envp);
>      else
> 

  ACK,

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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