From a399bc519ccf3f749e32a0eabfbb8db46780dd10 Mon Sep 17 00:00:00 2001
From: dongshengyuan <545258830@qq.com>
Date: Fri, 7 Aug 2026 13:37:51 +0800
Subject: [PATCH] man: mention openat2 effect of RestrictSUIDSGID

RestrictSUIDSGID uses seccomp to block setting SUID/SGID bits.
openat2() passes these mode bits indirectly via struct open_how.
Document that such calls are blocked regardless of requested mode.

Closes #43314
---
 man/systemd.exec.xml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index 0b43bc6960..7561425dc9 100644
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -2818,6 +2818,11 @@ RestrictNamespaces=~cgroup net</programlisting>
         <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, which
         defaults to off.</para>
 
+        <para>This setting is implemented using seccomp filtering. For system calls where the mode bits are
+        passed directly as arguments, the call is denied only when the SUID or SGID bits are set. For system
+        calls where those bits are passed indirectly and cannot be inspected by the filter, such as
+        <function>openat2()</function>, the call is blocked entirely, regardless of the requested mode.</para>
+
         <xi:include href="version-info.xml" xpointer="v242"/></listitem>
       </varlistentry>