Re: [PATCH] docs: landlock: clarify F_SETOWN signal scoping

The signal scope check for asynchronous I/O notifications uses the
Landlock domain saved when fcntl(F_SETOWN) configures the recipient.
Adding LANDLOCK_SCOPE_SIGNAL later therefore does not retroactively
restrict these pre-existing registrations.

Document this boundary in the IPC scoping section and link to the fcntl
documentation for I/O availability signaling.

Link: https://lore.kernel.org/linux-security-module/20261107.2f1fa9977739@gnoack.org/ (local)
Suggested-by: Günther Noack <redacted>
Signed-off-by: Shi Lecun <redacted>
---
 Documentation/userspace-api/landlock.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
index 3d45b956b640..cc9c5b102b8d 100644
--- a/Documentation/userspace-api/landlock.rst
+++ b/Documentation/userspace-api/landlock.rst

@@ -499,6 +499,10 @@ The operations which can be scoped are:
     This limits the sending of signals to target processes which run within the
     same or a nested Landlock domain.
 
+    For signaling of I/O availability (:manpage:`F_GETSIG(2const)`), Landlock
+    checks are done with respect to the Landlock domain at the time of
+    ``fcntl(F_SETOWN)``.
+
 ``LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET``
     This limits the set of abstract :manpage:`unix(7)` sockets to which we can
     :manpage:`connect(2)` to socket addresses which were created by a process in

base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.56.0