The opened file should be closed before return, otherwise resource leak
will occur.

Signed-off-by: Ding Xiang <dingxiang@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20230830101148.3738-1-dingxiang@cmss.chinamobile.com
Fixes: 3de64b656b3c ("selftests/landlock: Add supports_filesystem() helper")
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Add tests for the hostfs filesystems to make sure it has a consistent
inode management, which is required for Landlock's file hierarchy
identification.  This adds 5 new tests for layout3_fs with the hostfs
variant.

Add hostfs to the new (architecture-specific) config.um file.

The hostfs filesystem, only available for an User-Mode Linux kernel, is
special because we cannot explicitly mount it.  The layout3_fs.hostfs
variant tests are skipped if the current test directory is not backed by
this filesystem.

The layout3_fs.hostfs.tag_inode_dir_child and
layout3_fs.hostfs.tag_inode_file tests pass thanks to a previous commit
fixing hostfs inode management.  Without this fix, the deny-by-default
policy would apply and all access requests would be denied.

Link: https://lore.kernel.org/r/20230612191430.339153-7-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Add generic and read-only tests for 6 pseudo filesystems to make sure
they have a consistent inode management, which is required for
Landlock's file hierarchy identification:
- tmpfs
- ramfs
- cgroup2
- proc
- sysfs

Update related kernel configuration to support these new filesystems,
remove useless CONFIG_SECURITY_PATH, and sort all entries.  If these
filesystems are not supported by the kernel running tests, the related
tests are skipped.

Expanding variants, this adds 25 new tests for layout3_fs:
- tag_inode_dir_parent
- tag_inode_dir_mnt
- tag_inode_dir_child
- tag_inode_dir_file
- release_inodes

Test coverage for security/landlock with kernel debug code:
- 94.7% of 835 lines according to gcc/gcov-12
- 93.0% of 852 lines according to gcc/gcov-13

Test coverage for security/landlock without kernel debug code:
- 95.5% of 624 lines according to gcc/gcov-12
- 93.1% of 641 lines according to gcc/gcov-13

Link: https://lore.kernel.org/r/20230612191430.339153-6-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Add a new struct mnt_opt to define a mount point with the mount_opt()
helper.  This doesn't change tests but prepare for the next commit.

Link: https://lore.kernel.org/r/20230612191430.339153-5-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Replace supports_overlayfs() with supports_filesystem() to be able to
check several filesystems.  This will be useful in a following commit.

Only check for overlay filesystem once in the setup step, and then rely
on self->skip_test.

Cc: Guenter Roeck <groeck@chromium.org>
Cc: Jeff Xu <jeffxu@google.com>
Link: https://lore.kernel.org/r/20230612191430.339153-4-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Add and use a layout0 test fixture to not populate the tmpfs filesystem
if it is not required for tests: unknown_access_rights, proc_nsfs,
unpriv and max_layers.

This doesn't change these tests but it speeds up their setup and makes
them less prone to error.  This prepare the ground for a next commit.

Link: https://lore.kernel.org/r/20230612191430.339153-3-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Update ptrace tests according to all potential Yama security policies.
This is required to make such tests pass even if Yama is enabled.

Tests are not skipped but they now check both Landlock and Yama boundary
restrictions at run time to keep a maximum test coverage (i.e. positive
and negative testing).

Signed-off-by: Jeff Xu <jeffxu@google.com>
Link: https://lore.kernel.org/r/20230114020306.1407195-2-jeffxu@google.com
Cc: stable@vger.kernel.org
[mic: Add curly braces around EXPECT_EQ() to make it build, and improve
commit message]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>

overlayfs may be disabled in the kernel configuration, causing related
tests to fail.  Check that overlayfs is supported at runtime, so we can
skip layout2_overlay.* accordingly.

Signed-off-by: Jeff Xu <jeffxu@google.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230113053229.1281774-2-jeffxu@google.com
[mic: Reword comments and constify variables]
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Pull landlock updates from Mickaël Salaün:
 "This adds file truncation support to Landlock, contributed by Günther
  Noack. As described by Günther [1], the goal of these patches is to
  work towards a more complete coverage of file system operations that
  are restrictable with Landlock.

  The known set of currently unsupported file system operations in
  Landlock is described at [2]. Out of the operations listed there,
  truncate is the only one that modifies file contents, so these patches
  should make it possible to prevent the direct modification of file
  contents with Landlock.

  The new LANDLOCK_ACCESS_FS_TRUNCATE access right covers both the
  truncate(2) and ftruncate(2) families of syscalls, as well as open(2)
  with the O_TRUNC flag. This includes usages of creat() in the case
  where existing regular files are overwritten.

  Additionally, this introduces a new Landlock security blob associated
  with opened files, to track the available Landlock access rights at
  the time of opening the file. This is in line with Unix's general
  approach of checking the read and write permissions during open(), and
  associating this previously checked authorization with the opened
  file. An ongoing patch documents this use case [3].

  In order to treat truncate(2) and ftruncate(2) calls differently in an
  LSM hook, we split apart the existing security_path_truncate hook into
  security_path_truncate (for truncation by path) and
  security_file_truncate (for truncation of previously opened files)"

Link: https://lore.kernel.org/r/20221018182216.301684-1-gnoack3000@gmail.com [1]
Link: https://www.kernel.org/doc/html/v6.1/userspace-api/landlock.html#filesystem-flags [2]
Link: https://lore.kernel.org/r/20221209193813.972012-1-mic@digikod.net [3]

* tag 'landlock-6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
  samples/landlock: Document best-effort approach for LANDLOCK_ACCESS_FS_REFER
  landlock: Document Landlock's file truncation support
  samples/landlock: Extend sample tool to support LANDLOCK_ACCESS_FS_TRUNCATE
  selftests/landlock: Test ftruncate on FDs created by memfd_create(2)
  selftests/landlock: Test FD passing from restricted to unrestricted processes
  selftests/landlock: Locally define __maybe_unused
  selftests/landlock: Test open() and ftruncate() in multiple scenarios
  selftests/landlock: Test file truncation support
  landlock: Support file truncation
  landlock: Document init_layer_masks() helper
  landlock: Refactor check_access_path_dual() into is_access_to_paths_allowed()
  security: Create file_truncate hook from path_truncate hook

The only (forced) static test binary doesn't depend on libcap.  Because
using -lcap on systems that don't have such static library would fail
(e.g. on Arch Linux), let's be more specific and require only dynamic
libcap linking.

Fixes: a52540522c95 ("selftests/landlock: Fix out-of-tree builds")
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: Guillaume Tucker <guillaume.tucker@collabora.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20221019200536.2771316-1-mic@digikod.net