sd-event: add sd_event_source_disable_unref() helper

(cherry picked from commit afd15bbb4b6414b9356799c63029e36642dae8e4)
Related: CVE-2020-1712

2 files changed, 22 insertions, 12 deletions

diff --git a/man/rules/meson.build b/man/rules/meson.build
index 989d11c9b9..7ae94ea265 100644
--- a/man/rules/meson.build
+++ b/man/rules/meson.build
@@ -340,7 +340,9 @@ manpages = [
  ['sd_event_source_set_userdata', '3', ['sd_event_source_get_userdata'], ''],
  ['sd_event_source_unref',
   '3',
-  ['sd_event_source_ref', 'sd_event_source_unrefp'],
+  ['sd_event_source_disable_unref',
+   'sd_event_source_ref',
+   'sd_event_source_unrefp'],
   ''],
  ['sd_event_wait',
   '3',
diff --git a/man/sd_event_source_unref.xml b/man/sd_event_source_unref.xml
index d1b83c57aa..af8fed33f2 100644
--- a/man/sd_event_source_unref.xml
+++ b/man/sd_event_source_unref.xml
@@ -22,6 +22,7 @@
     <refname>sd_event_source_unref</refname>
     <refname>sd_event_source_unrefp</refname>
     <refname>sd_event_source_ref</refname>
+    <refname>sd_event_source_disable_unref</refname>
 
     <refpurpose>Increase or decrease event source reference counters</refpurpose>
   </refnamediv>
@@ -45,6 +46,10 @@
         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
       </funcprototype>
 
+      <funcprototype>
+        <funcdef>sd_event_source* <function>sd_event_source_disable_unref</function></funcdef>
+        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+      </funcprototype>
     </funcsynopsis>
   </refsynopsisdiv>
 
@@ -80,23 +85,26 @@
     the passed event source object is
     <constant>NULL</constant>.</para>
 
-    <para>Note that event source objects stay alive and may be
-    dispatched as long as they have a reference counter greater than
-    zero. In order to drop a reference of an event source and make
-    sure the associated event source handler function is not called
-    anymore it is recommended to combine a call of
+    <para>Note that event source objects stay alive and may be dispatched as long as they have a reference
+    counter greater than zero. In order to drop a reference of an event source and make sure the associated
+    event source handler function is not called anymore it is recommended to combine a call of
     <function>sd_event_source_unref()</function> with a prior call to
-    <function>sd_event_source_set_enabled()</function> with
-    <constant>SD_EVENT_OFF</constant>.</para>
+    <function>sd_event_source_set_enabled()</function> with <constant>SD_EVENT_OFF</constant> or call
+    <function>sd_event_source_disable_unref()</function>, see below.</para>
+
+    <para><function>sd_event_source_disable_unref()</function> combines a call to
+    <function>sd_event_source_set_enabled()</function> with <constant>SD_EVENT_OFF</constant> with
+    <function>sd_event_source_unref()</function>. This ensures that the source is disabled before the local
+    reference to it is lost. The <parameter>source</parameter> parameter is allowed to be
+    <constant>NULL</constant>.</para>
   </refsect1>
 
   <refsect1>
     <title>Return Value</title>
 
-    <para><function>sd_event_source_unref()</function> always returns
-    <constant>NULL</constant>.
-    <function>sd_event_source_ref()</function> always returns the
-    event source object passed in.</para>
+    <para><function>sd_event_source_unref()</function> and
+    <function>sd_event_source_disable_unref()</function> always return <constant>NULL</constant>.
+    <function>sd_event_source_ref()</function> always returns the event source object passed in.</para>
   </refsect1>
 
   <xi:include href="libsystemd-pkgconfig.xml" />