From: Ruediger Meier <ruediger.meier@ga-group.nl>
Date: Wed, 11 Jun 2014 15:31:56 +0000 (+0200)
Subject: utmpdump: fix localtime() error handling
X-Git-Tag: v2.25-rc1~28^2~6
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=18df1cc77c20acf0d80cc5c5ef38afa2f3fa148e;p=thirdparty%2Futil-linux.git

utmpdump: fix localtime() error handling

If current TZ has no representation of a given time_t then localtime()
would return NULL and break the next strftime().

In practice this happens very likely on systems with 64bit time_t when
parsing broken binary data. Seen on aarch64 (and probably s390) using
our (incompatible) test wtmp data.

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
---

diff --git a/login-utils/utmpdump.c b/login-utils/utmpdump.c
index 7611c9f0ac..e1fefc63e4 100644
--- a/login-utils/utmpdump.c
+++ b/login-utils/utmpdump.c
@@ -48,9 +48,10 @@
 static char *timetostr(const time_t time)
 {
 	static char s[29];	/* [Sun Sep 01 00:00:00 1998 PST] */
+	struct tm *tmp;
 
-	if (time != 0)
-		strftime(s, 29, "%a %b %d %T %Y %Z", localtime(&time));
+	if (time != 0 && (tmp = localtime(&time)))
+		strftime(s, 29, "%a %b %d %T %Y %Z", tmp);
 	else
 		s[0] = '\0';