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

[Corey Bryant <coreyb@linux.vnet.ibm.com>]

On 10/17/2012 09:15 AM, Eduardo Otubo wrote:
> 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 <otubo@linux.vnet.ibm.com>
> ---
>   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;
>

I think you need to either remove "TAP" from these messages, or limit 
this new code to tap and bridge since those are the backends that call 
execve().

Also, this should be documented somewhere so that users can find out 
about this behavior before attempting to hotplug a network device. 
Perhaps this could be documented on the man page for -sandbox and notes 
could be added to the HMP/QMP commands.

-- 
Regards,
Corey Bryant