From 9b2dad78f267ab3944d8b1145e3efe6c97bef4cf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Koutn=C3=BD?= <mkoutny@suse.com>
Date: Fri, 2 Nov 2018 20:56:08 +0100
Subject: [PATCH] core: Detect initial timer state from serialized data

We keep a mark whether a single-shot timer was triggered in the caller's
variable initial. When such a timer elapses while we are
serializing/deserializing the inner state, we consider the timer
incorrectly as elapsed and don't trigger it later.

This patch exploits last_trigger timestamp that we already serialize,
hence we can eliminate the argument initial completely.

A reproducer for OnBootSec= timers:
        cat >repro.c <<EOD
        /*
         * Compile:	gcc repro.c -o repro
         * Run:		./repro
         */
        #include <errno.h>
        #include <fcntl.h>
        #include <stdio.h>
        #include <stdlib.h>
        #include <sys/stat.h>
        #include <sys/types.h>
        #include <time.h>
        #include <unistd.h>

        int main(int argc, char *argv[]) {
        	char command[1024];
        	int pause;

        	struct timespec now;

        	while (1) {
        		usleep(rand() % 200000); // prevent periodic repeats
               		clock_gettime(CLOCK_MONOTONIC, &now);
        		printf("%i\n", now.tv_sec);

        		system("rm -f $PWD/mark");
        		snprintf(command, 1024, "systemd-run --user --on-boot=%i --timer-property=AccuracySec=100ms "
        					"touch $PWD/mark", now.tv_sec + 1);
        		system(command);
        		system("systemctl --user list-timers");
        		pause = (1000000000 - now.tv_nsec)/1000 - 70000; // fiddle to hit the middle of reloading
        		usleep(pause > 0 ? pause : 0);
        		system("systemctl --user daemon-reload");
        		sync();
        		sleep(2);
        		if (open("./mark", 0) < 0)
        			if (errno == ENOENT) {
        				printf("mark file does not exist\n");
        				break;
        			}
        	}

        	return 0;
        }
        EOD

(cherry picked from commit aa1f95d2647197eca84c33a0f10adaeada08467d)

Resolves: #1764908
---
 src/core/timer.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/core/timer.c b/src/core/timer.c
index fb192d558a..b36700c186 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -267,10 +267,10 @@ static void timer_set_state(Timer *t, TimerState state) {
         unit_notify(UNIT(t), state_translation_table[old_state], state_translation_table[state], true);
 }
 
-static void timer_enter_waiting(Timer *t, bool initial);
+static void timer_enter_waiting(Timer *t);
 
 static int timer_enter_waiting_coldplug(Unit *u) {
-        timer_enter_waiting(TIMER(u), false);
+        timer_enter_waiting(TIMER(u));
         return 0;
 }
 
@@ -338,7 +338,7 @@ static void add_random(Timer *t, usec_t *v) {
         log_unit_debug(UNIT(t)->id, "Adding %s random time.", format_timespan(s, sizeof(s), add, 0));
 }
 
-static void timer_enter_waiting(Timer *t, bool initial) {
+static void timer_enter_waiting(Timer *t) {
         bool found_monotonic = false, found_realtime = false;
         usec_t ts_realtime, ts_monotonic;
         usec_t base = 0;
@@ -442,7 +442,7 @@ static void timer_enter_waiting(Timer *t, bool initial) {
 
                         v->next_elapse = base + v->value;
 
-                        if (!initial && v->next_elapse < ts_monotonic && IN_SET(v->base, TIMER_ACTIVE, TIMER_BOOT, TIMER_STARTUP)) {
+                        if (dual_timestamp_is_set(&t->last_trigger) && v->next_elapse < ts_monotonic && IN_SET(v->base, TIMER_ACTIVE, TIMER_BOOT, TIMER_STARTUP)) {
                                 /* This is a one time trigger, disable it now */
                                 v->disabled = true;
                                 continue;
@@ -619,7 +619,7 @@ static int timer_start(Unit *u) {
         }
 
         t->result = TIMER_SUCCESS;
-        timer_enter_waiting(t, true);
+        timer_enter_waiting(t);
         return 1;
 }
 
@@ -742,14 +742,14 @@ static void timer_trigger_notify(Unit *u, Unit *other) {
         case TIMER_ELAPSED:
 
                 /* Recalculate sleep time */
-                timer_enter_waiting(t, false);
+                timer_enter_waiting(t);
                 break;
 
         case TIMER_RUNNING:
 
                 if (UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
                         log_unit_debug(UNIT(t)->id, "%s got notified about unit deactivation.", UNIT(t)->id);
-                        timer_enter_waiting(t, false);
+                        timer_enter_waiting(t);
                 }
                 break;
 
@@ -782,7 +782,7 @@ static void timer_time_change(Unit *u) {
                 return;
 
         log_unit_debug(u->id, "%s: time change, recalculating next elapse.", u->id);
-        timer_enter_waiting(t, false);
+        timer_enter_waiting(t);
 }
 
 static const char* const timer_state_table[_TIMER_STATE_MAX] = {