1 files changed, 55 insertions, 0 deletions
diff --git a/debian/patches/shared-calendarspec-abort-calculation-after-1000-iteratio.patch b/debian/patches/shared-calendarspec-abort-calculation-after-1000-iteratio.patch
new file mode 100644
index 0000000..49562a7
--- /dev/null
+++ b/debian/patches/shared-calendarspec-abort-calculation-after-1000-iteratio.patch
@@ -0,0 +1,55 @@
+From: =?utf-8?q?Zbigniew_J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
+Date: Sun, 21 Mar 2021 20:59:32 +0100
+Subject: shared/calendarspec: abort calculation after 1000 iterations
+
+We have a bug where we seem to enter an infinite loop when running in the
+Europe/Dublin timezone. The timezone is "special" because it has negative SAVE
+values. The handling of this should obviously be fixed, but let's use a
+belt-and-suspenders approach, and gracefully fail if we fail to find an answer
+within a specific number of attempts. The code in this function is rather
+complex, and it's hard to rule out another bug in the future.
+
+(cherry picked from commit 169615c9a8cdc54d748d4dfc8279be9b3c2bec44)
+---
+ src/shared/calendarspec.c | 14 +++++++++++++-
+ 1 file changed, 13 insertions(+), 1 deletion(-)
+
+diff --git a/src/shared/calendarspec.c b/src/shared/calendarspec.c
+index 7162592..80acc57 100644
+--- a/src/shared/calendarspec.c
++++ b/src/shared/calendarspec.c
+@@ -1211,6 +1211,10 @@ static bool matches_weekday(int weekdays_bits, const struct tm *tm, bool utc) {
+         return (weekdays_bits & (1 << k));
+ }
+ 
++/* A safety valve: if we get stuck in the calculation, return an error.
++ * C.f. https://bugzilla.redhat.com/show_bug.cgi?id=1941335. */
++#define MAX_CALENDAR_ITERATIONS 1000
++
+ static int find_next(const CalendarSpec *spec, struct tm *tm, usec_t *usec) {
+         struct tm c;
+         int tm_usec;
+@@ -1224,7 +1228,7 @@ static int find_next(const CalendarSpec *spec, struct tm *tm, usec_t *usec) {
+         c = *tm;
+         tm_usec = *usec;
+ 
+-        for (;;) {
++        for (unsigned iteration = 0; iteration < MAX_CALENDAR_ITERATIONS; iteration++) {
+                 /* Normalize the current date */
+                 (void) mktime_or_timegm(&c, spec->utc);
+                 c.tm_isdst = spec->dst;
+@@ -1321,6 +1325,14 @@ static int find_next(const CalendarSpec *spec, struct tm *tm, usec_t *usec) {
+                 *usec = tm_usec;
+                 return 0;
+         }
++
++        /* It seems we entered an infinite loop. Let's gracefully return an error instead of hanging or
++         * aborting. This code is also exercised when timers.target is brought up during early boot, so
++         * aborting here is problematic and hard to diagnose for users. */
++        _cleanup_free_ char *s = NULL;
++        (void) calendar_spec_to_string(spec, &s);
++        return log_warning_errno(SYNTHETIC_ERRNO(EDEADLK),
++                                 "Infinite loop in calendar calculation: %s", strna(s));
+ }
+ 
+ static int calendar_spec_next_usec_impl(const CalendarSpec *spec, usec_t usec, usec_t *ret_next) {