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author | Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> | 2021-03-21 20:59:32 +0100 |
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committer | Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> | 2021-03-23 10:01:17 +0100 |
commit | f14b80e09e225ccf7cfd8a85578b7e64c3fdebb9 (patch) | |
tree | 23e0fa3d8882e9fb0b424c052c91277478d038e1 | |
parent | 78415ea9f7de25fc883af980e91fbffadd5a38b5 (diff) | |
download | systemd-f14b80e09e225ccf7cfd8a85578b7e64c3fdebb9.tar.gz |
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)
-rw-r--r-- | src/shared/calendarspec.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/src/shared/calendarspec.c b/src/shared/calendarspec.c index 7162592fbf..80acc57800 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) { |