ppc: add host-serial and host-model machine attributes (CVE-2019-8934)

On ppc hosts, hypervisor shares following system attributes

  - /proc/device-tree/system-id
  - /proc/device-tree/model

with a guest. This could lead to information leakage and misuse.[*]
Add machine attributes to control such system information exposure
to a guest.

[*] https://wiki.openstack.org/wiki/OSSN/OSSN-0028

Reported-by: Daniel P. Berrangé <berrange@redhat.com>
Fix-suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Message-Id: <20190218181349.23885-1-ppandit@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 70 insertions, 6 deletions

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index abf9ebc..b3631e2 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1247,13 +1247,30 @@ static void *spapr_build_fdt(sPAPRMachineState *spapr)
      * Add info to guest to indentify which host is it being run on
      * and what is the uuid of the guest
      */
-    if (kvmppc_get_host_model(&buf)) {
-        _FDT(fdt_setprop_string(fdt, 0, "host-model", buf));
-        g_free(buf);
+    if (spapr->host_model && !g_str_equal(spapr->host_model, "none")) {
+        if (g_str_equal(spapr->host_model, "passthrough")) {
+            /* -M host-model=passthrough */
+            if (kvmppc_get_host_model(&buf)) {
+                _FDT(fdt_setprop_string(fdt, 0, "host-model", buf));
+                g_free(buf);
+            }
+        } else {
+            /* -M host-model=<user-string> */
+            _FDT(fdt_setprop_string(fdt, 0, "host-model", spapr->host_model));
+        }
     }
-    if (kvmppc_get_host_serial(&buf)) {
-        _FDT(fdt_setprop_string(fdt, 0, "host-serial", buf));
-        g_free(buf);
+
+    if (spapr->host_serial && !g_str_equal(spapr->host_serial, "none")) {
+        if (g_str_equal(spapr->host_serial, "passthrough")) {
+            /* -M host-serial=passthrough */
+            if (kvmppc_get_host_serial(&buf)) {
+                _FDT(fdt_setprop_string(fdt, 0, "host-serial", buf));
+                g_free(buf);
+            }
+        } else {
+            /* -M host-serial=<user-string> */
+            _FDT(fdt_setprop_string(fdt, 0, "host-serial", spapr->host_serial));
+        }
     }
 
     buf = qemu_uuid_unparse_strdup(&qemu_uuid);
@@ -3144,6 +3161,36 @@ static void spapr_set_ic_mode(Object *obj, const char *value, Error **errp)
     }
 }
 
+static char *spapr_get_host_model(Object *obj, Error **errp)
+{
+    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
+
+    return g_strdup(spapr->host_model);
+}
+
+static void spapr_set_host_model(Object *obj, const char *value, Error **errp)
+{
+    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
+
+    g_free(spapr->host_model);
+    spapr->host_model = g_strdup(value);
+}
+
+static char *spapr_get_host_serial(Object *obj, Error **errp)
+{
+    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
+
+    return g_strdup(spapr->host_serial);
+}
+
+static void spapr_set_host_serial(Object *obj, const char *value, Error **errp)
+{
+    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
+
+    g_free(spapr->host_serial);
+    spapr->host_serial = g_strdup(value);
+}
+
 static void spapr_instance_init(Object *obj)
 {
     sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
@@ -3189,6 +3236,17 @@ static void spapr_instance_init(Object *obj)
     object_property_set_description(obj, "ic-mode",
                  "Specifies the interrupt controller mode (xics, xive, dual)",
                  NULL);
+
+    object_property_add_str(obj, "host-model",
+        spapr_get_host_model, spapr_set_host_model,
+        &error_abort);
+    object_property_set_description(obj, "host-model",
+        "Set host's model-id to use - none|passthrough|string", &error_abort);
+    object_property_add_str(obj, "host-serial",
+        spapr_get_host_serial, spapr_set_host_serial,
+        &error_abort);
+    object_property_set_description(obj, "host-serial",
+        "Set host's system-id to use - none|passthrough|string", &error_abort);
 }
 
 static void spapr_machine_finalizefn(Object *obj)
@@ -4086,9 +4144,15 @@ DEFINE_SPAPR_MACHINE(4_0, "4.0", true);
 static void spapr_machine_3_1_class_options(MachineClass *mc)
 {
     sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
+    static GlobalProperty compat[] = {
+        { TYPE_SPAPR_MACHINE, "host-model", "passthrough" },
+        { TYPE_SPAPR_MACHINE, "host-serial", "passthrough" },
+    };
 
     spapr_machine_4_0_class_options(mc);
     compat_props_add(mc->compat_props, hw_compat_3_1, hw_compat_3_1_len);
+    compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat));
+
     mc->default_cpu_type = POWERPC_CPU_TYPE_NAME("power8_v2.0");
     smc->update_dt_enabled = false;
 }