From 17fe57d8dcc89aea520788914b252cf49cf060ff Mon Sep 17 00:00:00 2001
From: "Ondrej Zajicek (work)" <santiago@crfreenet.org>
Date: Tue, 1 Nov 2016 11:37:49 +0100
Subject: [PATCH] Log: Fix broken syslog name

BIRD passed string from configuration to openlog(), which kept it
internally. After reconfiguration the old string was freed, therefore
openlog had invalid copy.

Thanks to Chris Caputo for the original patch.
---
 lib/string.h      |  9 +++++++++
 sysdep/unix/log.c | 18 +++++++++++-------
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/lib/string.h b/lib/string.h
index 9af49b9e..bf0b7cb0 100644
--- a/lib/string.h
+++ b/lib/string.h
@@ -30,6 +30,15 @@ static inline char *xbasename(const char *str)
   return s ? s+1 : (char *) str;
 }
 
+static inline char *
+xstrdup(const char *c)
+{
+  size_t l = strlen(c) + 1;
+  char *z = xmalloc(l);
+  memcpy(z, c, l);
+  return z;
+}
+
 #define ROUTER_ID_64_LENGTH 23
 
 #endif
diff --git a/sysdep/unix/log.c b/sysdep/unix/log.c
index 1fd64426..b89e6b7a 100644
--- a/sysdep/unix/log.c
+++ b/sysdep/unix/log.c
@@ -288,18 +288,22 @@ log_switch(int debug, list *l, char *new_syslog_name)
   current_log_list = l;
 
 #ifdef HAVE_SYSLOG
-  char *old_syslog_name = current_syslog_name;
-  current_syslog_name = new_syslog_name;
-
-  if (old_syslog_name && new_syslog_name &&
-      !strcmp(old_syslog_name, new_syslog_name))
+  if (current_syslog_name && new_syslog_name &&
+      !strcmp(current_syslog_name, new_syslog_name))
     return;
 
-  if (old_syslog_name)
+  if (current_syslog_name)
+  {
     closelog();
+    xfree(current_syslog_name);
+    current_syslog_name = NULL;
+  }
 
   if (new_syslog_name)
-    openlog(new_syslog_name, LOG_CONS | LOG_NDELAY, LOG_DAEMON);
+  {
+    current_syslog_name = xstrdup(new_syslog_name);
+    openlog(current_syslog_name, LOG_CONS | LOG_NDELAY, LOG_DAEMON);
+  }
 #endif
 }