From: David Herrmann <dh.herrmann@gmail.com>
Date: Sat, 5 Sep 2015 10:56:04 +0000 (+0200)
Subject: login: fix NULL-deref on wall_message
X-Git-Tag: v226.4~1^2~82
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=ba5bb9837fda291f45cffa97fe8347e045a93694

login: fix NULL-deref on wall_message

We treat an empty wall-message equal to a NULL wall-message since:

        commit 5744f59a3ee883ef3a78214bd5236157acdc35ba
        Author: Lennart Poettering <lennart@poettering.net>
        Date:   Fri Sep 4 10:34:47 2015 +0200

            logind: treat an empty wall message like a NULL one

Fix the shutdown scheduler to not deref a NULL pointer, but properly
check for an empty wall-message.

Fixes: #1120
---

diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index cdb3007ac..def9f3927 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -1783,9 +1783,11 @@ static int update_schedule_file(Manager *m) {
         if (r < 0)
                 return log_error_errno(r, "Failed to create shutdown subdirectory: %m");
 
-        t = cescape(m->wall_message);
-        if (!t)
-                return log_oom();
+        if (!isempty(m->wall_message)) {
+                t = cescape(m->wall_message);
+                if (!t)
+                        return log_oom();
+        }
 
         r = fopen_temporary("/run/systemd/shutdown/scheduled", &f, &temp_path);
         if (r < 0)
@@ -1801,7 +1803,7 @@ static int update_schedule_file(Manager *m) {
                 m->enable_wall_messages,
                 m->scheduled_shutdown_type);
 
-        if (!isempty(m->wall_message))
+        if (t)
                 fprintf(f, "WALL_MESSAGE=%s\n", t);
 
         r = fflush_and_check(f);