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[71.132.185.69]) by smtp.gmail.com with ESMTPSA id 00721157ae682-78fb43701c7sm35628707b3.8.2025.12.21.11.43.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 21 Dec 2025 11:43:21 -0800 (PST) From: Justin Suess To: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Cc: Tingmao Wang , =?UTF-8?q?G=C3=BCnther=20Noack?= , Justin Suess , Jan Kara , Abhinav Saxena , linux-security-module@vger.kernel.org Subject: [PATCH v6 6/6] landlock: Add documentation for LANDLOCK_ADD_RULE_NO_INHERIT Date: Sun, 21 Dec 2025 14:43:01 -0500 Message-ID: <20251221194301.247484-7-utilityemal77@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251221194301.247484-1-utilityemal77@gmail.com> References: <20251221194301.247484-1-utilityemal77@gmail.com> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Adds documentation of the flag to the userspace api, describing the functionality of the flag and parent directory protections. Signed-off-by: Justin Suess --- Notes: v5..v6 changes: * None v1..v5 changes: * Initial addition Documentation/userspace-api/landlock.rst | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst index 1d0c2c15c22e..3671cd90fbe2 100644 --- a/Documentation/userspace-api/landlock.rst +++ b/Documentation/userspace-api/landlock.rst @@ -604,6 +604,23 @@ Landlock audit events with the ``LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF``, sys_landlock_restrict_self(). See Documentation/admin-guide/LSM/landlock.rst for more details on audit. +Filesystem inheritance suppression (ABI < 8) +----------------- + +Starting with the Landlock ABI version 8, it is possible to prevent a directory +or file from inheriting it's parent's access grants by using the +``LANDLOCK_ADD_RULE_NO_INHERIT`` flag passed to sys_landlock_add_rule(). This +can be useful for policies where a parent directory needs broader access than its +children. + +To mitigate sandbox-restart attacks, the inode itself, and ancestors of inodes +tagged with ``LANDLOCK_ADD_RULE_NO_INHERIT`` cannot be removed, renamed, +reparented, or linked into/from other directories. + +These parent directory protections propagate up to the root. Further inheritance +for grants originating beneath a ``LANDLOCK_ADD_RULE_NO_INHERIT`` tagged inode +are not affected unless also tagged with this flag. + .. _kernel_support: Kernel support -- 2.51.0