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qemu/backends/dbus-vmstate.c
Priyankar Jain 2748583211 dbus-vmstate: Restrict error checks to registered proxies in dbus_get_proxies 
The purpose of dbus_get_proxies to construct the proxies corresponding to the
IDs registered to dbus-vmstate.

Currenty, this function returns an error in case there is any failure
while instantiating proxy for "all" the names on dbus.

Ideally this function should error out only if it is not able to find and
validate the proxies registered to the backend otherwise any offending
process(for eg: the process purposefully may not export its Id property on
the dbus) may connect to the dbus and can lead to migration failures.

This commit ensures that dbus_get_proxies returns an error if it is not
able to find and validate the proxies of interest(the IDs registered
during the dbus-vmstate instantiation).

Signed-off-by: Priyankar Jain <priyankar.jain@nutanix.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1637936117-37977-1-git-send-email-priyankar.jain@nutanix.com>
2022-08-18 10:35:44 +04:00

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/*
* QEMU dbus-vmstate
*
* Copyright (C) 2019 Red Hat Inc
*
* Authors:
* Marc-André Lureau <marcandre.lureau@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qemu/units.h"
#include "qemu/dbus.h"
#include "qemu/error-report.h"
#include "qapi/error.h"
#include "qom/object_interfaces.h"
#include "qapi/qmp/qerror.h"
#include "migration/vmstate.h"
#include "trace.h"
#include "qom/object.h"
#define TYPE_DBUS_VMSTATE "dbus-vmstate"
OBJECT_DECLARE_SIMPLE_TYPE(DBusVMState,
DBUS_VMSTATE)
struct DBusVMState {
Object parent;
GDBusConnection *bus;
char *dbus_addr;
char *id_list;
uint32_t data_size;
uint8_t *data;
};
static const GDBusPropertyInfo vmstate_property_info[] = {
{ -1, (char *) "Id", (char *) "s",
G_DBUS_PROPERTY_INFO_FLAGS_READABLE, NULL },
};
static const GDBusPropertyInfo * const vmstate_property_info_pointers[] = {
&vmstate_property_info[0],
NULL
};
static const GDBusInterfaceInfo vmstate1_interface_info = {
-1,
(char *) "org.qemu.VMState1",
(GDBusMethodInfo **) NULL,
(GDBusSignalInfo **) NULL,
(GDBusPropertyInfo **) &vmstate_property_info_pointers,
NULL,
};
#define DBUS_VMSTATE_SIZE_LIMIT (1 * MiB)
static GHashTable *
get_id_list_set(DBusVMState *self)
{
g_auto(GStrv) ids = NULL;
g_autoptr(GHashTable) set = NULL;
int i;
if (!self->id_list) {
return NULL;
}
ids = g_strsplit(self->id_list, ",", -1);
set = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, NULL);
for (i = 0; ids[i]; i++) {
g_hash_table_add(set, ids[i]);
ids[i] = NULL;
}
return g_steal_pointer(&set);
}
static GHashTable *
dbus_get_proxies(DBusVMState *self, GError **err)
{
g_autoptr(GHashTable) proxies = NULL;
g_autoptr(GHashTable) ids = NULL;
g_auto(GStrv) names = NULL;
Error *error = NULL;
size_t i;
ids = get_id_list_set(self);
proxies = g_hash_table_new_full(g_str_hash, g_str_equal,
g_free, g_object_unref);
names = qemu_dbus_get_queued_owners(self->bus, "org.qemu.VMState1", &error);
if (!names) {
g_set_error(err, G_IO_ERROR, G_IO_ERROR_FAILED, "%s",
error_get_pretty(error));
error_free(error);
return NULL;
}
for (i = 0; names[i]; i++) {
g_autoptr(GDBusProxy) proxy = NULL;
g_autoptr(GVariant) result = NULL;
g_autofree char *id = NULL;
size_t size;
proxy = g_dbus_proxy_new_sync(self->bus, G_DBUS_PROXY_FLAGS_NONE,
(GDBusInterfaceInfo *) &vmstate1_interface_info,
names[i],
"/org/qemu/VMState1",
"org.qemu.VMState1",
NULL, err);
if (!proxy) {
if (err != NULL && *err != NULL) {
warn_report("%s: Failed to create proxy: %s",
__func__, (*err)->message);
g_clear_error(err);
}
continue;
}
result = g_dbus_proxy_get_cached_property(proxy, "Id");
if (!result) {
warn_report("%s: VMState Id property is missing.", __func__);
g_clear_object(&proxy);
continue;
}
id = g_variant_dup_string(result, &size);
if (ids && !g_hash_table_remove(ids, id)) {
g_clear_pointer(&id, g_free);
g_clear_object(&proxy);
continue;
}
if (size == 0 || size >= 256) {
g_set_error(err, G_IO_ERROR, G_IO_ERROR_FAILED,
"VMState Id '%s' is invalid.", id);
return NULL;
}
if (!g_hash_table_insert(proxies, id, proxy)) {
g_set_error(err, G_IO_ERROR, G_IO_ERROR_FAILED,
"Duplicated VMState Id '%s'", id);
return NULL;
}
id = NULL;
proxy = NULL;
g_clear_pointer(&result, g_variant_unref);
}
if (ids) {
g_autofree char **left = NULL;
left = (char **)g_hash_table_get_keys_as_array(ids, NULL);
if (*left) {
g_autofree char *leftids = g_strjoinv(",", left);
g_set_error(err, G_IO_ERROR, G_IO_ERROR_FAILED,
"Required VMState Id are missing: %s", leftids);
return NULL;
}
}
return g_steal_pointer(&proxies);
}
static int
dbus_load_state_proxy(GDBusProxy *proxy, const uint8_t *data, size_t size)
{
g_autoptr(GError) err = NULL;
g_autoptr(GVariant) result = NULL;
g_autoptr(GVariant) value = NULL;
value = g_variant_new_fixed_array(G_VARIANT_TYPE_BYTE,
data, size, sizeof(char));
result = g_dbus_proxy_call_sync(proxy, "Load",
g_variant_new("(@ay)",
g_steal_pointer(&value)),
G_DBUS_CALL_FLAGS_NO_AUTO_START,
-1, NULL, &err);
if (!result) {
error_report("%s: Failed to Load: %s", __func__, err->message);
return -1;
}
return 0;
}
static int dbus_vmstate_post_load(void *opaque, int version_id)
{
DBusVMState *self = DBUS_VMSTATE(opaque);
g_autoptr(GInputStream) m = NULL;
g_autoptr(GDataInputStream) s = NULL;
g_autoptr(GError) err = NULL;
g_autoptr(GHashTable) proxies = NULL;
uint32_t nelem;
trace_dbus_vmstate_post_load(version_id);
proxies = dbus_get_proxies(self, &err);
if (!proxies) {
error_report("%s: Failed to get proxies: %s", __func__, err->message);
return -1;
}
m = g_memory_input_stream_new_from_data(self->data, self->data_size, NULL);
s = g_data_input_stream_new(m);
g_data_input_stream_set_byte_order(s, G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN);
g_buffered_input_stream_set_buffer_size(G_BUFFERED_INPUT_STREAM(s),
DBUS_VMSTATE_SIZE_LIMIT);
nelem = g_data_input_stream_read_uint32(s, NULL, &err);
if (err) {
goto error;
}
while (nelem > 0) {
GDBusProxy *proxy = NULL;
uint32_t len;
gsize bytes_read, avail;
char id[256];
len = g_data_input_stream_read_uint32(s, NULL, &err);
if (err) {
goto error;
}
if (len >= 256) {
error_report("%s: Invalid DBus vmstate proxy name %u",
__func__, len);
return -1;
}
if (!g_input_stream_read_all(G_INPUT_STREAM(s), id, len,
&bytes_read, NULL, &err)) {
goto error;
}
if (bytes_read != len) {
error_report("%s: Short read", __func__);
return -1;
}
id[len] = 0;
trace_dbus_vmstate_loading(id);
proxy = g_hash_table_lookup(proxies, id);
if (!proxy) {
error_report("%s: Failed to find proxy Id '%s'", __func__, id);
return -1;
}
len = g_data_input_stream_read_uint32(s, NULL, &err);
if (len > DBUS_VMSTATE_SIZE_LIMIT) {
error_report("%s: Invalid vmstate size: %u", __func__, len);
return -1;
}
g_buffered_input_stream_fill(G_BUFFERED_INPUT_STREAM(s), len, NULL,
&err);
if (err) {
goto error;
}
avail = g_buffered_input_stream_get_available(
G_BUFFERED_INPUT_STREAM(s));
if (len > avail) {
error_report("%s: Not enough data available to load for Id: '%s'. "
"Available data size: %zu, Actual vmstate size: %u",
__func__, id, avail, len);
return -1;
}
if (dbus_load_state_proxy(proxy,
g_buffered_input_stream_peek_buffer(G_BUFFERED_INPUT_STREAM(s),
NULL),
len) < 0) {
error_report("%s: Failed to restore Id '%s'", __func__, id);
return -1;
}
if (!g_seekable_seek(G_SEEKABLE(s), len, G_SEEK_CUR, NULL, &err)) {
goto error;
}
nelem -= 1;
}
return 0;
error:
error_report("%s: Failed to read from stream: %s", __func__, err->message);
return -1;
}
static void
dbus_save_state_proxy(gpointer key,
gpointer value,
gpointer user_data)
{
GDataOutputStream *s = user_data;
const char *id = key;
GDBusProxy *proxy = value;
g_autoptr(GVariant) result = NULL;
g_autoptr(GVariant) child = NULL;
g_autoptr(GError) err = NULL;
const uint8_t *data;
gsize size;
trace_dbus_vmstate_saving(id);
result = g_dbus_proxy_call_sync(proxy, "Save",
NULL, G_DBUS_CALL_FLAGS_NO_AUTO_START,
-1, NULL, &err);
if (!result) {
error_report("%s: Failed to Save: %s", __func__, err->message);
return;
}
child = g_variant_get_child_value(result, 0);
data = g_variant_get_fixed_array(child, &size, sizeof(char));
if (!data) {
error_report("%s: Failed to Save: not a byte array", __func__);
return;
}
if (size > DBUS_VMSTATE_SIZE_LIMIT) {
error_report("%s: Too large vmstate data to save: %zu",
__func__, (size_t)size);
return;
}
if (!g_data_output_stream_put_uint32(s, strlen(id), NULL, &err) ||
!g_data_output_stream_put_string(s, id, NULL, &err) ||
!g_data_output_stream_put_uint32(s, size, NULL, &err) ||
!g_output_stream_write_all(G_OUTPUT_STREAM(s),
data, size, NULL, NULL, &err)) {
error_report("%s: Failed to write to stream: %s",
__func__, err->message);
}
}
static int dbus_vmstate_pre_save(void *opaque)
{
DBusVMState *self = DBUS_VMSTATE(opaque);
g_autoptr(GOutputStream) m = NULL;
g_autoptr(GDataOutputStream) s = NULL;
g_autoptr(GHashTable) proxies = NULL;
g_autoptr(GError) err = NULL;
trace_dbus_vmstate_pre_save();
proxies = dbus_get_proxies(self, &err);
if (!proxies) {
error_report("%s: Failed to get proxies: %s", __func__, err->message);
return -1;
}
m = g_memory_output_stream_new_resizable();
s = g_data_output_stream_new(m);
g_data_output_stream_set_byte_order(s, G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN);
if (!g_data_output_stream_put_uint32(s, g_hash_table_size(proxies),
NULL, &err)) {
error_report("%s: Failed to write to stream: %s",
__func__, err->message);
return -1;
}
g_hash_table_foreach(proxies, dbus_save_state_proxy, s);
if (g_memory_output_stream_get_size(G_MEMORY_OUTPUT_STREAM(m))
> UINT32_MAX) {
error_report("%s: DBus vmstate buffer is too large", __func__);
return -1;
}
if (!g_output_stream_close(G_OUTPUT_STREAM(m), NULL, &err)) {
error_report("%s: Failed to close stream: %s", __func__, err->message);
return -1;
}
g_free(self->data);
self->data_size =
g_memory_output_stream_get_size(G_MEMORY_OUTPUT_STREAM(m));
self->data =
g_memory_output_stream_steal_data(G_MEMORY_OUTPUT_STREAM(m));
return 0;
}
static const VMStateDescription dbus_vmstate = {
.name = TYPE_DBUS_VMSTATE,
.version_id = 0,
.pre_save = dbus_vmstate_pre_save,
.post_load = dbus_vmstate_post_load,
.fields = (VMStateField[]) {
VMSTATE_UINT32(data_size, DBusVMState),
VMSTATE_VBUFFER_ALLOC_UINT32(data, DBusVMState, 0, 0, data_size),
VMSTATE_END_OF_LIST()
}
};
static void
dbus_vmstate_complete(UserCreatable *uc, Error **errp)
{
DBusVMState *self = DBUS_VMSTATE(uc);
g_autoptr(GError) err = NULL;
if (!object_resolve_path_type("", TYPE_DBUS_VMSTATE, NULL)) {
error_setg(errp, "There is already an instance of %s",
TYPE_DBUS_VMSTATE);
return;
}
if (!self->dbus_addr) {
error_setg(errp, QERR_MISSING_PARAMETER, "addr");
return;
}
self->bus = g_dbus_connection_new_for_address_sync(self->dbus_addr,
G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT |
G_DBUS_CONNECTION_FLAGS_MESSAGE_BUS_CONNECTION,
NULL, NULL, &err);
if (err) {
error_setg(errp, "failed to connect to DBus: '%s'", err->message);
return;
}
if (vmstate_register(VMSTATE_IF(self), VMSTATE_INSTANCE_ID_ANY,
&dbus_vmstate, self) < 0) {
error_setg(errp, "Failed to register vmstate");
}
}
static void
dbus_vmstate_finalize(Object *o)
{
DBusVMState *self = DBUS_VMSTATE(o);
vmstate_unregister(VMSTATE_IF(self), &dbus_vmstate, self);
g_clear_object(&self->bus);
g_free(self->dbus_addr);
g_free(self->id_list);
g_free(self->data);
}
static char *
get_dbus_addr(Object *o, Error **errp)
{
DBusVMState *self = DBUS_VMSTATE(o);
return g_strdup(self->dbus_addr);
}
static void
set_dbus_addr(Object *o, const char *str, Error **errp)
{
DBusVMState *self = DBUS_VMSTATE(o);
g_free(self->dbus_addr);
self->dbus_addr = g_strdup(str);
}
static char *
get_id_list(Object *o, Error **errp)
{
DBusVMState *self = DBUS_VMSTATE(o);
return g_strdup(self->id_list);
}
static void
set_id_list(Object *o, const char *str, Error **errp)
{
DBusVMState *self = DBUS_VMSTATE(o);
g_free(self->id_list);
self->id_list = g_strdup(str);
}
static char *
dbus_vmstate_get_id(VMStateIf *vmif)
{
return g_strdup(TYPE_DBUS_VMSTATE);
}
static void
dbus_vmstate_class_init(ObjectClass *oc, void *data)
{
UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
VMStateIfClass *vc = VMSTATE_IF_CLASS(oc);
ucc->complete = dbus_vmstate_complete;
vc->get_id = dbus_vmstate_get_id;
object_class_property_add_str(oc, "addr",
get_dbus_addr, set_dbus_addr);
object_class_property_add_str(oc, "id-list",
get_id_list, set_id_list);
}
static const TypeInfo dbus_vmstate_info = {
.name = TYPE_DBUS_VMSTATE,
.parent = TYPE_OBJECT,
.instance_size = sizeof(DBusVMState),
.instance_finalize = dbus_vmstate_finalize,
.class_init = dbus_vmstate_class_init,
.interfaces = (InterfaceInfo[]) {
{ TYPE_USER_CREATABLE },
{ TYPE_VMSTATE_IF },
{ }
}
};
static void
register_types(void)
{
type_register_static(&dbus_vmstate_info);
}
type_init(register_types);
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