[PATCH v2 4/4] Landlock: Document LANDLOCK_SCOPED_SIGNAL

Improving Landlock ABI version 6 to support signal scoping
with LANDLOCK_SCOPED_SIGNAL.

Signed-off-by: Tahera Fahimi <[email protected]>
---
 Documentation/userspace-api/landlock.rst | 27 ++++++++++++++----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
index 01bd62dc6bb1..1923abfd2007 100644
--- a/Documentation/userspace-api/landlock.rst
+++ b/Documentation/userspace-api/landlock.rst
@@ -8,7 +8,7 @@ Landlock: unprivileged access control
 =====================================
 
 :Author: Mickaël Salaün
-:Date: July 2024
+:Date: August 2024
 
 The goal of Landlock is to enable to restrict ambient rights (e.g. global
 filesystem or network access) for a set of processes.  Because Landlock
@@ -82,7 +82,8 @@ to be explicit about the denied-by-default access rights.
             LANDLOCK_ACCESS_NET_BIND_TCP |
             LANDLOCK_ACCESS_NET_CONNECT_TCP,
         .scoped =
-            LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET,
+            LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET |
+            LANDLOCK_SCOPED_SIGNAL,
     };
 
 Because we may not know on which kernel version an application will be
@@ -123,7 +124,8 @@ version, and only use the available subset of access rights:
         ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV;
     case 5:
         /* Removes LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET for ABI < 6 */
-        ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET;
+        ruleset_attr.scoped &= ~(LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET |
+                                 LANDLOCK_SCOPED_SIGNAL);
     }
 
 This enables to create an inclusive ruleset that will contain our rules.
@@ -319,11 +321,14 @@ interactions between sandboxes. Each Landlock domain can be explicitly scoped
 for a set of actions by specifying it on a ruleset. For example, if a sandboxed
 process should not be able to :manpage:`connect(2)` to a non-sandboxed process
 through abstract :manpage:`unix(7)` sockets, we can specify such restriction
-with ``LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET``.
+with ``LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET``. Moreover, if a sandboxed process
+should not be able to send a signal to a non-sandboxed process, we can specify
+this restriction with ``LANDLOCK_SCOPED_SIGNAL``.
 
-A sandboxed process can connect to a non-sandboxed process when its domain is
-not scoped. If a process's domain is scoped, it can only connect to processes in
-the same scoped domain.
+A sandboxed process can access to a non-sandboxed process when its domain is
+not scoped. If a process's domain is scoped, it can only access to processes in
+the same scoped domain. For example, If a process is scoped to send signal to
+other processes, it can only send signals to processes in the same scoped domain.
 
 IPC scoping does not support Landlock rules, so if a domain is scoped, no rules
 can be added to allow accessing to a resource outside of the scoped domain.
@@ -563,12 +568,12 @@ earlier ABI.
 Starting with the Landlock ABI version 5, it is possible to restrict the use of
 :manpage:`ioctl(2)` using the new ``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right.
 
-Abstract Unix sockets Restriction  (ABI < 6)
---------------------------------------------
+Abstract Unix sockets and Signal Restriction  (ABI < 6)
+-------------------------------------------------------
 
 With ABI version 6, it is possible to restrict connection to an abstract Unix socket
-through ``LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET``, thanks to the ``scoped`` ruleset
-attribute.
+through ``LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET`` and sending signal through
+``LANDLOCK_SCOPED_SIGNAL``, thanks to the ``scoped`` ruleset attribute.
 
 .. _kernel_support:
 
-- 
2.34.1