From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 9 Jul 2014 19:20:58 +0200
Subject: sysusers: don't allow user names longer than UT_NAMESIZE
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As pointed out by Miloslav Trmač it might be a good idea to make sure
that usernames stay with in the utmp-defined limits.

(cherry picked from commit 932ad62b84165b0acf690ea34c4b8083657ae244)
---
 man/sysusers.d.xml      | 2 +-
 src/sysusers/sysusers.c | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/man/sysusers.d.xml b/man/sysusers.d.xml
index 549b3f6..40f8715 100644
--- a/man/sysusers.d.xml
+++ b/man/sysusers.d.xml
@@ -142,7 +142,7 @@ m authd input</programlisting>
                         <title>Name</title>
 
                         <para>The name field specifies the user or
-                        group name. It should be be shorter than 256
+                        group name. It should be be shorter than 31
                         characters and avoid any non-ASCII characters,
                         and not begin with a numeric character. It is
                         strongly recommended to pick user and group
diff --git a/src/sysusers/sysusers.c b/src/sysusers/sysusers.c
index c0af693..f3ba8cf 100644
--- a/src/sysusers/sysusers.c
+++ b/src/sysusers/sysusers.c
@@ -24,6 +24,7 @@
 #include <grp.h>
 #include <shadow.h>
 #include <getopt.h>
+#include <utmp.h>
 
 #include "util.h"
 #include "hashmap.h"
@@ -1095,6 +1096,9 @@ static bool valid_user_group_name(const char *u) {
         if ((size_t) (i-u) > (size_t) sz)
                 return false;
 
+        if ((size_t) (i-u) > UT_NAMESIZE - 1)
+                return false;
+
         return true;
 }
 
