From: Cristian Rodríguez <crrodriguez@opensuse.org>
Date: Sun, 15 Jan 2023 01:33:13 +0000 (+0000)
Subject: last: should not use errx/warnx on signal handlers
X-Git-Tag: v2.39-rc1~123^2~7
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=05bd23aade3a975826a933ee3b9fc2ad92d0a9c3;p=thirdparty%2Futil-linux.git

last: should not use errx/warnx on signal handlers

err/warn/et all are not async signal safe because they call
printf-like library functions that are never as-safe.

ctime_r is also not as-safe. you cannot use static storage
in the wrapper either, since access to it is not atomic.
---

diff --git a/login-utils/last.c b/login-utils/last.c
index 84629278e5..cc73d5840f 100644
--- a/login-utils/last.c
+++ b/login-utils/last.c
@@ -266,24 +266,14 @@ static int uread(FILE *fp, struct utmpx *u,  int *quit, const char *filename)
 }
 
 #ifndef FUZZ_TARGET
-/*
- *	Print a short date.
- */
-static char *showdate(void)
-{
-	static char s[CTIME_BUFSIZ];
-
-	ctime_r(&lastdate, s);
-	s[16] = 0;
-	return s;
-}
-
 /*
  *	SIGINT handler
  */
 static void int_handler(int sig __attribute__((unused)))
 {
-	errx(EXIT_FAILURE, _("Interrupted %s"), showdate());
+	/* can't use err on signal handler */
+	write(STDERR_FILENO, "Interrupted\n", sizeof("Interrupted\n")-1);
+	_exit(EXIT_FAILURE);
 }
 
 /*
@@ -291,7 +281,7 @@ static void int_handler(int sig __attribute__((unused)))
  */
 static void quit_handler(int sig __attribute__((unused)))
 {
-	warnx(_("Interrupted %s"), showdate());
+	write(STDERR_FILENO, "Interrupted\n", sizeof("Interrupted\n")-1);
 	signal(SIGQUIT, quit_handler);
 }
 #endif