Merge tag 'landlock-6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux

Pull landlock updates from Mickaël Salaün:
 "Some miscellaneous improvements, including new KUnit tests, extended
  documentation and boot help, and some cosmetic cleanups.

  Additional test changes already went through the net tree"

* tag 'landlock-6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
  samples/landlock: Don't error out if a file path cannot be opened
  landlock: Use f_cred in security_file_open() hook
  landlock: Rename "ptrace" files to "task"
  landlock: Simplify current_check_access_socket()
  landlock: Warn once if a Landlock action is requested while disabled
  landlock: Extend documentation for kernel support
  landlock: Add support for KUnit tests
  selftests/landlock: Clean up error logs related to capabilities

Author: torvalds

Documentation/userspace-api/landlock.rst

@@ -19,11 +19,12 @@ unexpected/malicious behaviors in user space applications.  Landlock empowers
 any process, including unprivileged ones, to securely restrict themselves.
 
 We can quickly make sure that Landlock is enabled in the running system by
-looking for "landlock: Up and running" in kernel logs (as root): ``dmesg | grep
-landlock || journalctl -kg landlock`` .  Developers can also easily check for
-Landlock support with a :ref:`related system call <landlock_abi_versions>`.  If
-Landlock is not currently supported, we need to :ref:`configure the kernel
-appropriately <kernel_support>`.
+looking for "landlock: Up and running" in kernel logs (as root):
+``dmesg | grep landlock || journalctl -kb -g landlock`` .
+Developers can also easily check for Landlock support with a
+:ref:`related system call <landlock_abi_versions>`.
+If Landlock is not currently supported, we need to
+:ref:`configure the kernel appropriately <kernel_support>`.
 
 Landlock rules
 ==============
@@ -499,6 +500,9 @@ access rights.
 Kernel support
 ==============
 
+Build time configuration
+------------------------
+
 Landlock was first introduced in Linux 5.13 but it must be configured at build
 time with ``CONFIG_SECURITY_LANDLOCK=y``.  Landlock must also be enabled at boot
 time as the other security modules.  The list of security modules enabled by
@@ -507,11 +511,52 @@ contains ``CONFIG_LSM=landlock,[...]`` with ``[...]``  as the list of other
 potentially useful security modules for the running system (see the
 ``CONFIG_LSM`` help).
 
+Boot time configuration
+-----------------------
+
 If the running kernel does not have ``landlock`` in ``CONFIG_LSM``, then we can
-still enable it by adding ``lsm=landlock,[...]`` to
-Documentation/admin-guide/kernel-parameters.rst thanks to the bootloader
+enable Landlock by adding ``lsm=landlock,[...]`` to
+Documentation/admin-guide/kernel-parameters.rst in the boot loader
 configuration.
 
+For example, if the current built-in configuration is:
+
+.. code-block:: console
+
+    $ zgrep -h "^CONFIG_LSM=" "/boot/config-$(uname -r)" /proc/config.gz 2>/dev/null
+    CONFIG_LSM="lockdown,yama,integrity,apparmor"
+
+...and if the cmdline doesn't contain ``landlock`` either:
+
+.. code-block:: console
+
+    $ sed -n 's/.*\(\<lsm=\S\+\).*/\1/p' /proc/cmdline
+    lsm=lockdown,yama,integrity,apparmor
+
+...we should configure the boot loader to set a cmdline extending the ``lsm``
+list with the ``landlock,`` prefix::
+
+  lsm=landlock,lockdown,yama,integrity,apparmor
+
+After a reboot, we can check that Landlock is up and running by looking at
+kernel logs:
+
+.. code-block:: console
+
+    # dmesg | grep landlock || journalctl -kb -g landlock
+    [    0.000000] Command line: [...] lsm=landlock,lockdown,yama,integrity,apparmor
+    [    0.000000] Kernel command line: [...] lsm=landlock,lockdown,yama,integrity,apparmor
+    [    0.000000] LSM: initializing lsm=lockdown,capability,landlock,yama,integrity,apparmor
+    [    0.000000] landlock: Up and running.
+
+The kernel may be configured at build time to always load the ``lockdown`` and
+``capability`` LSMs.  In that case, these LSMs will appear at the beginning of
+the ``LSM: initializing`` log line as well, even if they are not configured in
+the boot loader.
+
+Network support
+---------------
+
 To be able to explicitly allow TCP operations (e.g., adding a network rule with
 ``LANDLOCK_ACCESS_NET_BIND_TCP``), the kernel must support TCP
 (``CONFIG_INET=y``).  Otherwise, sys_landlock_add_rule() returns an

samples/landlock/sandboxer.c

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: BSD-3-Clause
 /*
- * Simple Landlock sandbox manager able to launch a process restricted by a
- * user-defined filesystem access control policy.
+ * Simple Landlock sandbox manager able to execute a process restricted by
+ * user-defined file system and network access control policies.
  *
  * Copyright © 2017-2020 Mickaël Salaün <[email protected]>
  * Copyright © 2020 ANSSI
@@ -120,9 +120,11 @@ static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,
 		if (path_beneath.parent_fd < 0) {
 			fprintf(stderr, "Failed to open \"%s\": %s\n",
 				path_list[i], strerror(errno));
-			goto out_free_name;
+			continue;
 		}
 		if (fstat(path_beneath.parent_fd, &statbuf)) {
+			fprintf(stderr, "Failed to stat \"%s\": %s\n",
+				path_list[i], strerror(errno));
 			close(path_beneath.parent_fd);
 			goto out_free_name;
 		}
@@ -227,7 +229,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
 			ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
 			ENV_TCP_CONNECT_NAME, argv[0]);
 		fprintf(stderr,
-			"Launch a command in a restricted environment.\n\n");
+			"Execute a command in a restricted environment.\n\n");
 		fprintf(stderr,
 			"Environment variables containing paths and ports "
 			"each separated by a colon:\n");
@@ -248,7 +250,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
 			ENV_TCP_CONNECT_NAME);
 		fprintf(stderr,
 			"\nexample:\n"
-			"%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "
+			"%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" "
 			"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
 			"%s=\"9418\" "
 			"%s=\"80:443\" "
@@ -383,6 +385,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
 
 	cmd_path = argv[1];
 	cmd_argv = argv + 1;
+	fprintf(stderr, "Executing the sandboxed command...\n");
 	execvpe(cmd_path, cmd_argv, envp);
 	fprintf(stderr, "Failed to execute \"%s\": %s\n", cmd_path,
 		strerror(errno));

security/landlock/.kunitconfig

@@ -0,0 +1,4 @@
+CONFIG_KUNIT=y
+CONFIG_SECURITY=y
+CONFIG_SECURITY_LANDLOCK=y
+CONFIG_SECURITY_LANDLOCK_KUNIT_TEST=y

security/landlock/Kconfig

@@ -20,3 +20,18 @@ config SECURITY_LANDLOCK
 	  If you are unsure how to answer this question, answer N.  Otherwise,
 	  you should also prepend "landlock," to the content of CONFIG_LSM to
 	  enable Landlock at boot time.
+
+config SECURITY_LANDLOCK_KUNIT_TEST
+	bool "KUnit tests for Landlock" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
+	depends on SECURITY_LANDLOCK
+	default KUNIT_ALL_TESTS
+	help
+	  Build KUnit tests for Landlock.
+
+	  See the KUnit documentation in Documentation/dev-tools/kunit
+
+	  Run all KUnit tests for Landlock with:
+	  ./tools/testing/kunit/kunit.py run --kunitconfig security/landlock
+
+	  If you are unsure how to answer this question, answer N.

security/landlock/Makefile

@@ -1,6 +1,6 @@
 obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
 
 landlock-y := setup.o syscalls.o object.o ruleset.o \
-	cred.o ptrace.o fs.o
+	cred.o task.o fs.o
 
 landlock-$(CONFIG_INET) += net.o

security/landlock/common.h

@@ -17,4 +17,6 @@
 
 #define pr_fmt(fmt) LANDLOCK_NAME ": " fmt
 
+#define BIT_INDEX(bit) HWEIGHT(bit - 1)
+
 #endif /* _SECURITY_LANDLOCK_COMMON_H */