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From: Marcel Moolenaar <marcel@FreeBSD.org>
Date: Sat, 5 Apr 2014 18:14:58 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r264161 - head/lib/libc/gen
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Author: marcel
Date: Sat Apr  5 18:14:58 2014
New Revision: 264161
URL: http://svnweb.freebsd.org/changeset/base/264161

Log:
  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

Modified:
  head/lib/libc/gen/getlogin.c

Modified: head/lib/libc/gen/getlogin.c
==============================================================================
--- head/lib/libc/gen/getlogin.c	Sat Apr  5 18:13:28 2014	(r264160)
+++ head/lib/libc/gen/getlogin.c	Sat Apr  5 18:14:58 2014	(r264161)
@@ -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);