time-util: refuse formatting/parsing times that we can't store

usec_t is always 64bit, which means it can cover quite a number of
years. However, 4 digit year display and glibc limitations around time_t
limit what we can actually parse and format. Let's make this explicit,
so that we never end up formatting dates we can#t parse and vice versa.

Note that this is really just about formatting/parsing. Internal
calculations with times outside of the formattable range are not
affected.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/shared/logs-show.c b/src/shared/logs-show.c
index 75ea25c8ac..72c43e80cb 100644
--- a/src/shared/logs-show.c
+++ b/src/shared/logs-show.c
@@ -246,6 +246,11 @@ static int output_timestamp_realtime(FILE *f, sd_journal *j, OutputMode mode, Ou
         if (r < 0)
                 return log_error_errno(r, "Failed to get realtime timestamp: %m");
 
+        if (x > USEC_TIMESTAMP_FORMATTABLE_MAX) {
+                log_error("Timestamp cannot be printed");
+                return -EINVAL;
+        }
+
         if (mode == OUTPUT_SHORT_FULL) {
                 const char *k;