Re: [PATCH] tools: Restrict configuration of qemu processes

[Jim Fehlig <jfehlig@suse.com>]

Opps, forgot to cc the tools maintainers, sorry. I can resend if needed.

Regards,
Jim

On 03/14/2016 07:08 PM, Jim Fehlig wrote:
> Commit 6ef823fd added '-nodefaults' to the qemu args created by
> libxl, which is a good step in restricting qemu's default
> configuration. This change takes another step by adding
> -no-user-config, which ignores any user-provided config files in
> sysconfdir. Together, -nodefaults and -no-user-config allow Xen
> to avoid unkown and uncontrolled qemu configuration.
>
> Both options are also added to the qemu invocation in the
> xen-qemu-dom0-disk-backend systemd service file.
>
> Signed-off-by: Jim Fehlig <jfehlig@suse.com>
> ---
>  tools/hotplug/Linux/systemd/xen-qemu-dom0-disk-backend.service.in | 1 +
>  tools/libxl/libxl_dm.c                                            | 6 ++++++
>  2 files changed, 7 insertions(+)
>
> diff --git a/tools/hotplug/Linux/systemd/xen-qemu-dom0-disk-backend.service.in b/tools/hotplug/Linux/systemd/xen-qemu-dom0-disk-backend.service.in
> index acf61a8..f56775b 100644
> --- a/tools/hotplug/Linux/systemd/xen-qemu-dom0-disk-backend.service.in
> +++ b/tools/hotplug/Linux/systemd/xen-qemu-dom0-disk-backend.service.in
> @@ -14,6 +14,7 @@ ExecStartPre=/bin/mkdir -p @XEN_RUN_DIR@
>  ExecStart=@qemu_xen_systemd@ -xen-domid 0 \
>  	-xen-attach -name dom0 -nographic -M xenpv -daemonize \
>  	-monitor /dev/null -serial /dev/null -parallel /dev/null \
> +	-nodefaults -no-user-config \
>  	-pidfile @XEN_RUN_DIR@/qemu-dom0.pid
>  
>  [Install]
> diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
> index 4aca38e..cfda24c 100644
> --- a/tools/libxl/libxl_dm.c
> +++ b/tools/libxl/libxl_dm.c
> @@ -828,6 +828,12 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
>       */
>      flexarray_append(dm_args, "-nodefaults");
>  
> +    /*
> +     * Do not use any of the user-provided config files in sysconfdir,
> +     * avoiding unkown and uncontrolled configuration.
> +     */
> +    flexarray_append(dm_args, "-no-user-config");
> +
>      if (b_info->type == LIBXL_DOMAIN_TYPE_PV) {
>          flexarray_append(dm_args, "-xen-attach");
>      }


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