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authorSimon McVittie <simon.mcvittie@collabora.co.uk>2015-06-17 16:45:49 +0100
committerSimon McVittie <simon.mcvittie@collabora.co.uk>2015-06-17 17:04:26 +0100
commit71161305f191d1fe1242ccca47657f9ab51caad4 (patch)
treea8bbcd7703e14af5556ca93a5ea492d467587510
parenteef8c1f6fd712749ff0204097eef9545d90842a2 (diff)
logind: save /run/systemd/users/UID before starting user@.service
Previously, this had a race condition during a user's first login. Some component calls CreateSession (most likely by a PAM service other than 'systemd-user' running pam_systemd), with the following results: - logind: * create the user's XDG_RUNTIME_DIR * tell pid 1 to create user-UID.slice * tell pid 1 to start user@UID.service Then these two processes race: - logind: * save information including XDG_RUNTIME_DIR to /run/systemd/users/UID - the subprocess of pid 1 responsible for user@service: * start a 'systemd-user' PAM session, which reads XDG_RUNTIME_DIR and puts it in the environment * run systemd --user, which requires XDG_RUNTIME_DIR in the environment If logind wins the race, which usually happens, everything is fine; but if the subprocesses of pid 1 win the race, which can happen under load, then systemd --user exits unsuccessfully. To avoid this race, we have to write out /run/systemd/users/UID even though the service has not "officially" started yet; previously this did an early-return without saving anything. Record its state as OPENING in this case. Bug: https://github.com/systemd/systemd/issues/232 Reviewed-by: Philip Withnall <philip.withnall@collabora.co.uk>
-rw-r--r--src/login/logind-user.c22
1 files changed, 17 insertions, 5 deletions
diff --git a/src/login/logind-user.c b/src/login/logind-user.c
index 6720899def..bfbdc9b1b8 100644
--- a/src/login/logind-user.c
+++ b/src/login/logind-user.c
@@ -105,7 +105,7 @@ void user_free(User *u) {
free(u);
}
-int user_save(User *u) {
+static int user_save_internal(User *u) {
_cleanup_free_ char *temp_path = NULL;
_cleanup_fclose_ FILE *f = NULL;
int r;
@@ -113,9 +113,6 @@ int user_save(User *u) {
assert(u);
assert(u->state_file);
- if (!u->started)
- return 0;
-
r = mkdir_safe_label("/run/systemd/users", 0755, 0, 0);
if (r < 0)
goto finish;
@@ -258,6 +255,15 @@ finish:
return r;
}
+int user_save(User *u) {
+ assert(u);
+
+ if (!u->started)
+ return 0;
+
+ return user_save_internal (u);
+}
+
int user_load(User *u) {
_cleanup_free_ char *display = NULL, *realtime = NULL, *monotonic = NULL;
Session *s = NULL;
@@ -453,6 +459,12 @@ int user_start(User *u) {
if (r < 0)
return r;
+ /* Save the user data so far, because pam_systemd will read the
+ * XDG_RUNTIME_DIR out of it while starting up systemd --user.
+ * We need to do user_save_internal() because we have not
+ * "officially" started yet. */
+ user_save_internal(u);
+
/* Spawn user systemd */
r = user_start_service(u);
if (r < 0)
@@ -704,7 +716,7 @@ UserState user_get_state(User *u) {
if (u->stopping)
return USER_CLOSING;
- if (u->slice_job || u->service_job)
+ if (!u->started || u->slice_job || u->service_job)
return USER_OPENING;
if (u->sessions) {