Prevent crash on dbus reconnection (#2186468)

dnsmasq-2.90-dbus-watchers-bz2186468.patch

@@ -0,0 +1,93 @@
+From 33635d8564f96cedcef9bf9826cbbca76f28aa81 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Petr=20Men=C5=A1=C3=ADk?= <pemensik@redhat.com>
+Date: Mon, 17 Apr 2023 20:55:31 +0100
+Subject: [PATCH] Fix crash in dbus code.
+
+If I configure dnsmasq to use dbus and then restart dbus.service with watchers present,
+it crashes dnsmasq. The reason is simple, it uses loop to walk over watchers to call
+dbus handling code. But from that code the same list can be modified and watchers removed.
+But the list iteration continues anyway.
+
+Restart the loop if list were modified.
+---
+ src/dbus.c | 24 ++++++++++++++++++++----
+ 1 file changed, 20 insertions(+), 4 deletions(-)
+
+diff --git a/src/dbus.c b/src/dbus.c
+index 24efcb8..34cf2f6 100644
+--- a/src/dbus.c
++++ b/src/dbus.c
+@@ -106,6 +106,7 @@ const char* introspection_xml_template =
+ "</node>\n";
+ 
+ static char *introspection_xml = NULL;
++static int watches_modified = 0;
+ 
+ struct watch {
+   DBusWatch *watch;      
+@@ -127,6 +128,7 @@ static dbus_bool_t add_watch(DBusWatch *watch, void *data)
+   w->watch = watch;
+   w->next = daemon->watches;
+   daemon->watches = w;
++  watches_modified++;
+ 
+   (void)data; /* no warning */
+   return TRUE;
+@@ -134,7 +136,7 @@ static dbus_bool_t add_watch(DBusWatch *watch, void *data)
+ 
+ static void remove_watch(DBusWatch *watch, void *data)
+ {
+-  struct watch **up, *w, *tmp;  
++  struct watch **up, *w, *tmp;
+   
+   for (up = &(daemon->watches), w = daemon->watches; w; w = tmp)
+     {
+@@ -143,6 +145,7 @@ static void remove_watch(DBusWatch *watch, void *data)
+ 	{
+ 	  *up = tmp;
+ 	  free(w);
++	  watches_modified++;
+ 	}
+       else
+ 	up = &(w->next);
+@@ -966,11 +969,11 @@ void set_dbus_listeners(void)
+       }
+ }
+ 
+-void check_dbus_listeners()
++static int check_dbus_watches()
+ {
+-  DBusConnection *connection = (DBusConnection *)daemon->dbus;
+   struct watch *w;
+ 
++  watches_modified = 0;
+   for (w = daemon->watches; w; w = w->next)
+     if (dbus_watch_get_enabled(w->watch))
+       {
+@@ -987,9 +990,22 @@ void check_dbus_listeners()
+ 	  flags |= DBUS_WATCH_ERROR;
+ 
+ 	if (flags != 0)
+-	  dbus_watch_handle(w->watch, flags);
++	  {
++	    dbus_watch_handle(w->watch, flags);
++	    if (watches_modified)
++	      return 0;
++	  }
+       }
+ 
++  return 1;
++}
++
++void check_dbus_listeners()
++{
++  DBusConnection *connection = (DBusConnection *)daemon->dbus;
++
++  while (!check_dbus_watches()) ;
++
+   if (connection)
+     {
+       dbus_connection_ref (connection);
+-- 
+2.40.0
+

dnsmasq.spec

@@ -23,7 +23,7 @@
 
 Name:           dnsmasq
 Version:        2.89
-Release:        4%{?extraversion:.%{extraversion}}%{?dist}
+Release:        5%{?extraversion:.%{extraversion}}%{?dist}
 Summary:        A lightweight DHCP/caching DNS server
 
 # SPDX identifiers already
@@ -47,6 +47,8 @@ Patch2:         dnsmasq-2.81-configuration.patch
 Patch3:         dnsmasq-2.78-fips.patch
 # https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;h=eb92fb32b746f2104b0f370b5b295bb8dd4bd5e5
 Patch4:         dnsmasq-2.89-edns0-size.patch
+# http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=33635d8564f96cedcef9bf9826cbbca76f28aa81
+Patch5:         dnsmasq-2.90-dbus-watchers-bz2186468.patch
 
 
 Requires:       nettle
@@ -217,6 +219,9 @@ install -Dpm 644 %{SOURCE2} %{buildroot}%{_sysusersdir}/%{name}.conf
 %endif
 
 %changelog
+* Thu Apr 27 2023 Petr Menšík <pemensik@redhat.com> - 2.89-5
+- Prevent crash on dbus reconnection (#2186468)
+
 * Thu Apr 27 2023 Petr Menšík <pemensik@redhat.com> - 2.89-4
 - Actually enable localization support in dnsmasq (#2131681)