man: document the default value of NoNewPrivileges=

Fixes #4329.

1 files changed, 16 insertions, 7 deletions

diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index dbe4594730..6a26f3c133 100644
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -1234,13 +1234,22 @@
       <varlistentry>
         <term><varname>NoNewPrivileges=</varname></term>
 
-        <listitem><para>Takes a boolean argument. If true, ensures
-        that the service process and all its children can never gain
-        new privileges. This option is more powerful than the
-        respective secure bits flags (see above), as it also prohibits
-        UID changes of any kind. This is the simplest, most effective
-        way to ensure that a process and its children can never
-        elevate privileges again.</para></listitem>
+        <listitem><para>Takes a boolean argument. If true, ensures that the service
+        process and all its children can never gain new privileges. This option is more
+        powerful than the respective secure bits flags (see above), as it also prohibits
+        UID changes of any kind. This is the simplest and most effective way to ensure that
+        a process and its children can never elevate privileges again. Defaults to false,
+        but in the user manager instance certain settings force
+        <varname>NoNewPrivileges=yes</varname>, ignoring the value of this setting.
+        Those is the case when <varname>SystemCallFilter=</varname>,
+        <varname>SystemCallArchitectures=</varname>,
+        <varname>RestrictAddressFamilies=</varname>,
+        <varname>PrivateDevices=</varname>,
+        <varname>ProtectKernelTunables=</varname>,
+        <varname>ProtectKernelModules=</varname>,
+        <varname>MemoryDenyWriteExecute=</varname>, or
+        <varname>RestrictRealtime=</varname> are specified.
+        </para></listitem>
       </varlistentry>
 
       <varlistentry>