From eef9f6d258acd453e4d709c0ef38a5c336f1744d Mon Sep 17 00:00:00 2001
From: Marcel Moolenaar <marcel@FreeBSD.org>
Date: Sat, 5 Apr 2014 18:14:58 +0000
Subject: [PATCH] The getlogin_basic() function can return a 0 status with a
 NULL pointer for the login name (result). Make sure to handle that case
 properly. Improve robustness by checking namelen and then nul-terminating the
 provided buffer to simplify subsequent logic.

Obtained from:	Juniper Networks, Inc.
MFC after:	1 week
---
 lib/libc/gen/getlogin.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/lib/libc/gen/getlogin.c b/lib/libc/gen/getlogin.c
index 4dab3cb07f2..7ab4cba88a4 100644
--- a/lib/libc/gen/getlogin.c
+++ b/lib/libc/gen/getlogin.c
@@ -87,11 +87,16 @@ getlogin_r(char *logname, int namelen)
 	char	*result;
 	int	len;
 	int	status;
-	
+
+	if (namelen < 1)
+		return (ERANGE);
+	logname[0] = '\0';
+
 	THREAD_LOCK();
 	result = getlogin_basic(&status);
-	if (status == 0) {
-		if ((len = strlen(result) + 1) > namelen)
+	if (status == 0 && result != NULL) {
+		len = strlen(result) + 1;
+		if (len > namelen)
 			status = ERANGE;
 		else
 			strncpy(logname, result, len);