Merge pull request #30612 from AdrianVovk/sleep-freeze-user-seesions

Freeze user sessions for all types of sleep

src/home/homework.c

@@ -4,11 +4,14 @@
 #include <sys/mount.h>
 
 #include "blockdev-util.h"
+#include "bus-unit-util.h"
 #include "chown-recursive.h"
 #include "copy.h"
+#include "env-util.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "filesystems.h"
+#include "format-util.h"
 #include "fs-util.h"
 #include "home-util.h"
 #include "homework-blob.h"
@@ -1820,8 +1823,37 @@ static int home_inspect(UserRecord *h, UserRecord **ret_home) {
         return 1;
 }
 
+static int user_session_freezer(uid_t uid, bool freeze_now, UnitFreezer *ret) {
+        _cleanup_free_ char *unit = NULL;
+        int r;
+
+        r = getenv_bool("SYSTEMD_HOME_LOCK_FREEZE_SESSION");
+        if (r < 0 && r != -ENXIO)
+                log_warning_errno(r, "Cannot parse value of $SYSTEMD_HOME_LOCK_FREEZE_SESSION, ignoring.");
+        else if (r == 0) {
+                if (freeze_now)
+                        log_notice("Session remains unfrozen on explicit request ($SYSTEMD_HOME_LOCK_FREEZE_SESSION "
+                                   "is set to false). This is not recommended, and might result in unexpected behavior "
+                                   "including data loss!");
+                *ret = (UnitFreezer) {};
+                return 0;
+        }
+
+        if (asprintf(&unit, "user-" UID_FMT ".slice", uid) < 0)
+                return log_oom();
+
+        if (freeze_now)
+                r = unit_freezer_new_freeze(unit, ret);
+        else
+                r = unit_freezer_new(unit, ret);
+        if (r < 0)
+                return r;
+        return 1;
+}
+
 static int home_lock(UserRecord *h) {
         _cleanup_(home_setup_done) HomeSetup setup = HOME_SETUP_INIT;
+        _cleanup_(unit_freezer_done_thaw) UnitFreezer freezer = {};
         int r;
 
         assert(h);
@@ -1837,16 +1869,27 @@ static int home_lock(UserRecord *h) {
         if (r != USER_TEST_MOUNTED)
                 return log_error_errno(SYNTHETIC_ERRNO(ENOEXEC), "Home directory of %s is not mounted, can't lock.", h->user_name);
 
+        r = user_session_freezer(h->uid, /* freeze_now= */ true, &freezer);
+        if (r < 0)
+                log_warning_errno(r, "Failed to freeze user session, ignoring: %m");
+        else if (r == 0)
+                log_info("User session freeze disabled, skipping.");
+        else
+                log_info("Froze user session.");
+
         r = home_lock_luks(h, &setup);
         if (r < 0)
                 return r;
 
+        unit_freezer_done(&freezer); /* Don't thaw the user session. */
+
         log_info("Everything completed.");
         return 1;
 }
 
 static int home_unlock(UserRecord *h) {
         _cleanup_(home_setup_done) HomeSetup setup = HOME_SETUP_INIT;
+        _cleanup_(unit_freezer_done_thaw) UnitFreezer freezer = {};
         _cleanup_(password_cache_free) PasswordCache cache = {};
         int r;
 
@@ -1868,6 +1911,11 @@ static int home_unlock(UserRecord *h) {
         if (r < 0)
                 return r;
 
+        /* We want to thaw the session only after it's safe to access $HOME */
+        r = user_session_freezer(h->uid, /* freeze_now= */ false, &freezer);
+        if (r < 0)
+                log_warning_errno(r, "Failed to recover freezer for user session, ignoring: %m");
+
         log_info("Everything completed.");
         return 1;
 }

src/shared/bus-unit-util.c

@@ -10,6 +10,7 @@
 #include "cgroup-setup.h"
 #include "cgroup-util.h"
 #include "condition.h"
+#include "constants.h"
 #include "coredump-util.h"
 #include "cpu-set-util.h"
 #include "dissect-image.h"
@@ -2937,3 +2938,89 @@ int bus_service_manager_reload(sd_bus *bus) {
 
         return 0;
 }
+
+int unit_freezer_new(const char *name, UnitFreezer *ret) {
+        _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+        _cleanup_free_ char *namedup = NULL;
+        int r;
+
+        assert(name);
+        assert(ret);
+
+        namedup = strdup(name);
+        if (!namedup)
+                return log_oom_debug();
+
+        r = bus_connect_system_systemd(&bus);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to open connection to systemd: %m");
+
+        (void) sd_bus_set_method_call_timeout(bus, FREEZE_TIMEOUT);
+
+        *ret = (UnitFreezer) {
+                .name = TAKE_PTR(namedup),
+                .bus = TAKE_PTR(bus),
+        };
+        return 0;
+}
+
+static int unit_freezer_action(bool freeze, UnitFreezer *f) {
+        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        int r;
+
+        assert(f);
+        assert(f->bus);
+        assert(f->name);
+
+        r = bus_call_method(f->bus, bus_systemd_mgr, freeze ? "FreezeUnit" : "ThawUnit",
+                            &error, NULL, "s", f->name);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to %s unit %s: %s", freeze ? "freeze" : "thaw",
+                                       f->name, bus_error_message(&error, r));
+
+        return 0;
+}
+
+int unit_freezer_freeze(UnitFreezer *f) {
+        return unit_freezer_action(true, f);
+}
+
+int unit_freezer_thaw(UnitFreezer *f) {
+        return unit_freezer_action(false, f);
+}
+
+void unit_freezer_done(UnitFreezer *f) {
+        assert(f);
+
+        f->name = mfree(f->name);
+        f->bus = sd_bus_flush_close_unref(f->bus);
+}
+
+int unit_freezer_new_freeze(const char *name, UnitFreezer *ret) {
+        _cleanup_(unit_freezer_done) UnitFreezer f = {};
+        int r;
+
+        assert(name);
+        assert(ret);
+
+        r = unit_freezer_new(name, &f);
+        if (r < 0)
+                return r;
+
+        r = unit_freezer_freeze(&f);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_STRUCT(f);
+        return 0;
+}
+
+void unit_freezer_done_thaw(UnitFreezer *f) {
+        assert(f);
+
+        if (!f->name)
+                return;
+
+        (void) unit_freezer_thaw(f);
+        unit_freezer_done(f);
+}

src/shared/bus-unit-util.h

@@ -35,3 +35,20 @@ int unit_load_state(sd_bus *bus, const char *name, char **load_state);
 int unit_info_compare(const UnitInfo *a, const UnitInfo *b);
 
 int bus_service_manager_reload(sd_bus *bus);
+
+typedef struct UnitFreezer {
+        char *name;
+        sd_bus *bus;
+} UnitFreezer;
+
+int unit_freezer_new(const char *name, UnitFreezer *ret);
+
+int unit_freezer_freeze(UnitFreezer *freezer);
+
+int unit_freezer_thaw(UnitFreezer *freezer);
+
+void unit_freezer_done(UnitFreezer *freezer);
+
+int unit_freezer_new_freeze(const char *name, UnitFreezer *ret);
+
+void unit_freezer_done_thaw(UnitFreezer *freezer);

src/sleep/sleep.c

@@ -23,10 +23,12 @@
 #include "build.h"
 #include "bus-error.h"
 #include "bus-locator.h"
+#include "bus-unit-util.h"
 #include "bus-util.h"
 #include "constants.h"
 #include "devnum-util.h"
 #include "efivars.h"
+#include "env-util.h"
 #include "exec-util.h"
 #include "fd-util.h"
 #include "fileio.h"
@@ -444,38 +446,11 @@ static int custom_timer_suspend(const SleepConfig *sleep_config) {
         return 1;
 }
 
-/* Freeze when invoked and thaw on cleanup */
-static int freeze_thaw_user_slice(const char **method) {
-        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
-        _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
-        int r;
-
-        if (!method || !*method)
-                return 0;
-
-        r = bus_connect_system_systemd(&bus);
-        if (r < 0)
-                return log_debug_errno(r, "Failed to open connection to systemd: %m");
-
-        (void) sd_bus_set_method_call_timeout(bus, FREEZE_TIMEOUT);
-
-        r = bus_call_method(bus, bus_systemd_mgr, *method, &error, NULL, "s", SPECIAL_USER_SLICE);
-        if (r < 0)
-                return log_debug_errno(r, "Failed to execute operation: %s", bus_error_message(&error, r));
-
-        return 1;
-}
-
 static int execute_s2h(const SleepConfig *sleep_config) {
-        _unused_ _cleanup_(freeze_thaw_user_slice) const char *auto_method_thaw = "ThawUnit";
         int r;
 
         assert(sleep_config);
 
-        r = freeze_thaw_user_slice(&(const char*) { "FreezeUnit" });
-        if (r < 0)
-                log_warning_errno(r, "Failed to freeze unit user.slice, ignoring: %m");
-
         /* Only check if we have automated battery alarms if HibernateDelaySec= is not set, as in that case
          * we'll busy poll for the configured interval instead */
         if (!timestamp_is_set(sleep_config->hibernate_delay_usec)) {
@@ -599,6 +574,7 @@ static int parse_argv(int argc, char *argv[]) {
 }
 
 static int run(int argc, char *argv[]) {
+        _cleanup_(unit_freezer_done_thaw) UnitFreezer user_slice_freezer = {};
         _cleanup_(sleep_config_freep) SleepConfig *sleep_config = NULL;
         int r;
 
@@ -617,6 +593,22 @@ static int run(int argc, char *argv[]) {
                                        "Sleep operation \"%s\" is disabled by configuration, refusing.",
                                        sleep_operation_to_string(arg_operation));
 
+        /* Freeze the user sessions */
+        r = getenv_bool("SYSTEMD_SLEEP_FREEZE_USER_SESSIONS");
+        if (r < 0 && r != -ENXIO)
+                log_warning_errno(r, "Cannot parse value of $SYSTEMD_SLEEP_FREEZE_USER_SESSIONS, ignoring.");
+        if (r != 0) {
+                r = unit_freezer_new_freeze(SPECIAL_USER_SLICE, &user_slice_freezer);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to freeze user sessions, ignoring: %m");
+                else
+                        log_info("Froze user sessions");
+        } else
+                log_notice("User sessions remain unfrozen on explicit request "
+                           "($SYSTEMD_SLEEP_FREEZE_USER_SESSIONS is set to false). This is not recommended, "
+                           "and might result in unexpected behavior, particularly in sysupend-then-hibernate "
+                           "operations or setups with encrypted home directories.");
+
         switch (arg_operation) {
 
         case SLEEP_SUSPEND_THEN_HIBERNATE: