Add a snprinf wrapper which checks that the buffer was big enough

If we scale our buffer to be wide enough for the format string, we
should expect that the calculation was correct.

char_array_0() invocations are removed, since snprintf nul-terminates
the output in any case.

A similar wrapper is used for strftime calls, but only in timedatectl.c.

1 files changed, 4 insertions, 5 deletions

diff --git a/src/journal/journald-kmsg.c b/src/journal/journald-kmsg.c
index aca4571ece..0b02eff6ef 100644
--- a/src/journal/journald-kmsg.c
+++ b/src/journal/journald-kmsg.c
@@ -40,7 +40,8 @@ void server_forward_kmsg(
         const struct ucred *ucred) {
 
         struct iovec iovec[5];
-        char header_priority[6], header_pid[16];
+        char header_priority[4],
+             header_pid[sizeof("[]: ")-1 + DECIMAL_STR_MAX(pid_t) + 1];
         int n = 0;
         char *ident_buf = NULL;
 
@@ -60,8 +61,7 @@ void server_forward_kmsg(
         priority = syslog_fixup_facility(priority);
 
         /* First: priority field */
-        snprintf(header_priority, sizeof(header_priority), "<%i>", priority);
-        char_array_0(header_priority);
+        xsprintf(header_priority, "<%i>", priority);
         IOVEC_SET_STRING(iovec[n++], header_priority);
 
         /* Second: identifier and PID */
@@ -71,8 +71,7 @@ void server_forward_kmsg(
                         identifier = ident_buf;
                 }
 
-                snprintf(header_pid, sizeof(header_pid), "["PID_FMT"]: ", ucred->pid);
-                char_array_0(header_pid);
+                xsprintf(header_pid, "["PID_FMT"]: ", ucred->pid);
 
                 if (identifier)
                         IOVEC_SET_STRING(iovec[n++], identifier);