From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Thu, 7 Jul 2022 18:27:02 +0900
Subject: time-util: fix buffer-over-run

Fixes #23928.

(cherry picked from commit 9102c625a673a3246d7e73d8737f3494446bad4e)
(cherry picked from commit 72d4c15a946d20143cd4c6783c802124bc894dc7)
(cherry picked from commit c32530f5bdd11c74e8f5a86eecd7c36b3bae739f)
(cherry picked from commit b2a25b5e64345bd0bb7697a956d33afd6980286a)
(cherry picked from commit 858dc1ad609290cc4ca288acf87046ee295c3d51)
---
 src/basic/time-util.c     | 2 +-
 src/test/test-time-util.c | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/basic/time-util.c b/src/basic/time-util.c
index 5318d63..1909710 100644
--- a/src/basic/time-util.c
+++ b/src/basic/time-util.c
@@ -574,7 +574,7 @@ char *format_timespan(char *buf, size_t l, usec_t t, usec_t accuracy) {
                         t = b;
                 }
 
-                n = MIN((size_t) k, l);
+                n = MIN((size_t) k, l-1);
 
                 l -= n;
                 p += n;
diff --git a/src/test/test-time-util.c b/src/test/test-time-util.c
index cc391e8..877b24c 100644
--- a/src/test/test-time-util.c
+++ b/src/test/test-time-util.c
@@ -243,6 +243,13 @@ static void test_format_timespan(usec_t accuracy) {
         test_format_timespan_one(USEC_INFINITY, accuracy);
 }
 
+static void test_format_timespan2(void) {
+        /* See issue #23928. */
+        _cleanup_free_ char *buf;
+        assert_se(buf = new(char, 5));
+        assert_se(buf == format_timespan(buf, 5, 100005, 1000));
+}
+
 static void test_timezone_is_valid(void) {
         log_info("/* %s */", __func__);
 
@@ -533,6 +540,7 @@ int main(int argc, char *argv[]) {
         test_format_timespan(1);
         test_format_timespan(USEC_PER_MSEC);
         test_format_timespan(USEC_PER_SEC);
+        test_format_timespan2();
         test_timezone_is_valid();
         test_get_timezones();
         test_usec_add();