Re: [Qemu-devel] [PATCH 4/4] Warning messages on net devices hotplug

[Corey Bryant]

On 10/18/2012 11:15 AM, Paolo Bonzini wrote:
> Il 17/10/2012 15:15, Eduardo Otubo ha scritto:
> > With the inclusion of the new "double whitelist" seccomp filter, Qemu
> > won't be able to execve() in runtime, thus, no hotplug net devices
> > allowed.
> >
> > Signed-off-by: Eduardo Otubo <address@hidden>
>
> Please check this in net_init_tap instead.  When using libvirt, hotplug
> is done with a completely different mechanism that involves
> file-descriptor passing and does not require executing a helper.
>
> Paolo

Are you sure net_init_tap() is the right place for this check?  We only 
want to prevent execve() after main_loop() is entered.  In other words 
we want to allow execve() caused by a command line option (e.g. -net 
tap) but we want to prevent execve() when it is the result of a monitor 
command (e.g. netdev_add tap).

> > ---
> >   hmp.c |  6 ++++++
> >   net.c | 13 +++++++++++++
> >   2 files changed, 19 insertions(+)
> >
> > diff --git a/hmp.c b/hmp.c
> > index 70bdec2..f258338 100644
> > --- a/hmp.c
> > +++ b/hmp.c
> > @@ -1091,6 +1091,12 @@ void hmp_netdev_add(Monitor *mon, const QDict *qdict)
> >       Error *err = NULL;
> >       QemuOpts *opts;
> >
> > +#ifdef CONFIG_SECCOMP
> > +    error_set(&err, ERROR_CLASS_GENERIC_ERROR,
> > +            "Cannot hotplug TAP device when -sandbox is in effect");
> > +    goto out;
> > +#endif
> > +
> >       opts = qemu_opts_from_qdict(qemu_find_opts("netdev"), qdict, &err);
> >       if (error_is_set(&err)) {
> >           goto out;
> > diff --git a/net.c b/net.c
> > index ae4bc0d..a652ee9 100644
> > --- a/net.c
> > +++ b/net.c
> > @@ -752,6 +752,12 @@ void net_host_device_add(Monitor *mon, const QDict *qdict)
> >       Error *local_err = NULL;
> >       QemuOpts *opts;
> >
> > +#ifdef CONFIG_SECCOMP
> > +    error_set(&local_err, ERROR_CLASS_GENERIC_ERROR,
> > +            "Cannot hotplug TAP device when -sandbox is in effect");
> > +    goto out;
> > +#endif
> > +
> >       if (!net_host_check_device(device)) {
> >           monitor_printf(mon, "invalid host network device %s\n", device);
> >           return;
> > @@ -765,6 +771,7 @@ void net_host_device_add(Monitor *mon, const QDict *qdict)
> >       qemu_opt_set(opts, "type", device);
> >
> >       net_client_init(opts, 0, &local_err);
> > +out:
> >       if (error_is_set(&local_err)) {
> >           qerror_report_err(local_err);
> >           error_free(local_err);
> > @@ -800,6 +807,12 @@ int qmp_netdev_add(Monitor *mon, const QDict *qdict, 
> > QObject **ret)
> >       QemuOptsList *opts_list;
> >       QemuOpts *opts;
> >
> > +#ifdef CONFIG_SECCOMP
> > +    error_set(&local_err, ERROR_CLASS_GENERIC_ERROR,
> > +            "Cannot hotplug TAP device when -sandbox is in effect");
> > +    goto exit_err;
> > +#endif
> > +
> >       opts_list = qemu_find_opts_err("netdev", &local_err);
> >       if (error_is_set(&local_err)) {
> >           goto exit_err;

--
Regards,
Corey Bryant