core: use usec_add() at one more place

Follow-up for 8af1b296cb2cec8ddbb2cb47f4194269eb6cee2b.
Fixes CID#1590317.

diff --git a/src/core/exec-invoke.c b/src/core/exec-invoke.c
index 7f79ae4962c1b4e88f6288ae310fc9daa23ae915..4332bd23e53c34a85bde969012d063c5450223ac 100644 (file)
--- a/src/core/exec-invoke.c
+++ b/src/core/exec-invoke.c
@@ -1117,7 +1117,7 @@ static int ask_password_conv(
                                 .credential = credential_name,
                                 .tty_fd = -EBADF,
                                 .hup_fd = -EBADF,
-                                .until = now(CLOCK_MONOTONIC) + 15 * USEC_PER_SEC,
+                                .until = usec_add(now(CLOCK_MONOTONIC), 15 * USEC_PER_SEC),
                         };
 
                         _cleanup_(strv_free_erasep) char **acquired = NULL;