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nm-sudo: fix race during exit-on-idle

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nm-sudo is D-Bus activated and exits-on-idle. To do that race-free we
need:

  - sd_notify("STOPPING=1")
  - ReleaseName
  - keep processing pending requests
This commit is contained in:
Thomas Haller 2021-08-02 22:30:47 +02:00
parent 5d9a46ad34
commit a210e9a6f4
No known key found for this signature in database
GPG key ID: 29C2366E4DFC5728
2 changed files with 62 additions and 10 deletions
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1
data/nm-sudo.service.in
View file

@ -18,6 +18,7 @@ Description=NetworkManager Sudo Helper
Type=dbus
BusName=org.freedesktop.nm.sudo
ExecStart=@libexecdir@/nm-sudo
NotifyAccess=main
# Extra configuration options. Set via `systemctl edit nm-sudo.service`:
#

71
src/nm-sudo/nm-sudo.c
View file

@ -5,10 +5,11 @@
#include <gio/gunixfdlist.h>
#include "c-list/src/c-list.h"
#include "libnm-glib-aux/nm-dbus-aux.h"
#include "libnm-glib-aux/nm-io-utils.h"
#include "libnm-glib-aux/nm-logging-base.h"
#include "libnm-glib-aux/nm-shared-utils.h"
#include "libnm-glib-aux/nm-time-utils.h"
#include "libnm-glib-aux/nm-dbus-aux.h"
#include "libnm-base/nm-sudo-utils.h"
/* nm-sudo doesn't link with libnm-core nor libnm-base, but these headers
@ -50,6 +51,7 @@ struct _GlobalData {
guint32 timeout_msec;
bool name_owner_initialized;
bool service_registered;
bool name_requested;
/* This is controlled by $NM_SUDO_NO_AUTH_FOR_TESTING. It disables authentication
* of the request, so it is ONLY for testing. */
@ -401,6 +403,10 @@ _bus_register_service(GlobalData *gl)
.is_waiting = TRUE,
};
/* regardless whether the request is successful, after we start calling
* RequestName, we remember that we need to ReleaseName it. */
gl->name_requested = TRUE;
g_dbus_connection_call(
gl->dbus_connection,
DBUS_SERVICE_DBUS,
@ -412,7 +418,7 @@ _bus_register_service(GlobalData *gl)
(guint) (DBUS_NAME_FLAG_ALLOW_REPLACEMENT | DBUS_NAME_FLAG_REPLACE_EXISTING)),
G_VARIANT_TYPE("(u)"),
G_DBUS_CALL_FLAGS_NONE,
-1,
10000,
gl->quit_cancellable,
_bus_register_service_request_name_cb,
&data);
@ -505,6 +511,16 @@ _pending_job_register_object(GlobalData *gl, GObject *obj)
/*****************************************************************************/
static void
_bus_release_name_cb(GObject *source, GAsyncResult *result, gpointer user_data)
{
_nm_unused gs_unref_object GObject *keep_alive_object = user_data;
g_main_context_wakeup(NULL);
}
/*****************************************************************************/
static void
_initial_setup(GlobalData *gl)
{
@ -582,14 +598,49 @@ main(int argc, char **argv)
while (TRUE) {
if (!c_list_is_empty(&gl->pending_jobs_lst_head)) {
/* we must first reply to all requests. No matter what. */
} else {
if (gl->is_shutting_down_quitting || gl->is_shutting_down_timeout) {
/* we either hit the idle timeout or received SIGTERM. Note that
* if we received an idle-timeout and the very moment afterwards
* a new request, then _bus_method_call() will clear gl->is_shutting_down_timeout
* (via _pending_job_register_object()). */
break;
} else if (gl->is_shutting_down_quitting || gl->is_shutting_down_timeout) {
/* we either hit the idle timeout or received SIGTERM. Note that
* if we received an idle-timeout and the very moment afterwards
* a new request, then _bus_method_call() will clear gl->is_shutting_down_timeout
* (via _pending_job_register_object()). */
if (gl->name_requested) {
gs_unref_object GObject *keep_alive_object = g_object_new(G_TYPE_OBJECT, NULL);
/* We already requested a name. To exit-on-idle without race, we need to dance.
* See https://lists.freedesktop.org/archives/dbus/2015-May/016671.html . */
gl->name_requested = FALSE;
gl->is_shutting_down_quitting = TRUE;
_LOGT("shutdown: release-name");
/* we use the _pending_job_register_object() mechanism to make the loop busy during
* shutdown. */
_pending_job_register_object(gl, keep_alive_object);
r = nm_sd_notify("STOPPING=1");
if (r < 0)
_LOGW("shutdown: sd_notifiy(STOPPING=1) failed: %s", nm_strerror_native(-r));
else
_LOGT("shutdown: sd_notifiy(STOPPING=1) succeeded");
g_dbus_connection_call(gl->dbus_connection,
DBUS_SERVICE_DBUS,
DBUS_PATH_DBUS,
DBUS_INTERFACE_DBUS,
"ReleaseName",
g_variant_new("(s)", NM_SUDO_DBUS_BUS_NAME),
G_VARIANT_TYPE("(u)"),
G_DBUS_CALL_FLAGS_NONE,
10000,
NULL,
_bus_release_name_cb,
g_steal_pointer(&keep_alive_object));
continue;
}
break;
}
g_main_context_iteration(NULL, TRUE);
@ -597,7 +648,7 @@ main(int argc, char **argv)
done:
gl->is_shutting_down_cleanup = TRUE;
_LOGD("exiting...");
_LOGD("shutdown: cleanup");
nm_assert(c_list_is_empty(&gl->pending_jobs_lst_head));