[Xen-devel] [PATCH] tools: Restrict configuration of qemu processes

[Jim Fehlig <jfehlig@xxxxxxxx>]

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@xxxxxxxx>
---
 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");
     }
-- 
2.1.4


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