selftests: kselftest_harness: save full exit code in metadata

Instead of tracking passed = 0/1 rename the field to exit_code
and invert the values so that they match the KSFT_* exit codes.
This will allow us to fold SKIP / XFAIL into the same value.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

landlock: Support network rules with TCP bind and connect

Add network rules support in the ruleset management helpers and the
landlock_create_ruleset() syscall. Extend user space API to support
network actions:
* Add new network access rights: LANDLOCK_ACCESS_NET_BIND_TCP and
LANDLOCK_ACCESS_NET_CONNECT_TCP.
* Add a new network rule type: LANDLOCK_RULE_NET_PORT tied to struct
landlock_net_port_attr. The allowed_access field contains the network
access rights, and the port field contains the port value according to
the controlled protocol. This field can take up to a 64-bit value
but the maximum value depends on the related protocol (e.g. 16-bit
value for TCP). Network port is in host endianness [1].
* Add a new handled_access_net field to struct landlock_ruleset_attr
that contains network access rights.
* Increment the Landlock ABI version to 4.

Implement socket_bind() and socket_connect() LSM hooks, which enable
to control TCP socket binding and connection to specific ports.

Expand access_masks_t from u16 to u32 to be able to store network access
rights alongside filesystem access rights for rulesets' handled access
rights.

Access rights are not tied to socket file descriptors but checked at
bind() or connect() call time against the caller's Landlock domain. For
the filesystem, a file descriptor is a direct access to a file/data.
However, for network sockets, we cannot identify for which data or peer
a newly created socket will give access to. Indeed, we need to wait for
a connect or bind request to identify the use case for this socket.
Likewise a directory file descriptor may enable to open another file
(i.e. a new data item), but this opening is also restricted by the
caller's domain, not the file descriptor's access rights [2].

[1] https://lore.kernel.org/r/278ab07f-7583-a4e0-3d37-1bacd091531d@digikod.net
[2] https://lore.kernel.org/r/263c1eb3-602f-57fe-8450-3f138581bee7@digikod.net

Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-9-konstantin.meskhidze@huawei.com
[mic: Extend commit message, fix typo in comments, and specify
endianness in the documentation]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>

selftests/landlock: Test FD passing from restricted to unrestricted processes

A file descriptor created in a restricted process carries Landlock
restrictions with it which will apply even if the same opened file is
used from an unrestricted process.

This change extracts suitable FD-passing helpers from base_test.c and
moves them to common.h. We use the fixture variants from the ftruncate
fixture to exercise the same scenarios as in the open_and_ftruncate
test, but doing the Landlock restriction and open() in a different
process than the ftruncate() call.

Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20221018182216.301684-9-gnoack3000@gmail.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>

landlock: Support file truncation

Introduce the LANDLOCK_ACCESS_FS_TRUNCATE flag for file truncation.

This flag hooks into the path_truncate, file_truncate and
file_alloc_security LSM hooks and covers file truncation using
truncate(2), ftruncate(2), open(2) with O_TRUNC, as well as creat().

This change also increments the Landlock ABI version, updates
corresponding selftests, and updates code documentation to document
the flag.

In security/security.c, allocate security blobs at pointer-aligned
offsets. This fixes the problem where one LSM's security blob can
shift another LSM's security blob to an unaligned address (reported
by Nathan Chancellor).

The following operations are restricted:

open(2): requires the LANDLOCK_ACCESS_FS_TRUNCATE right if a file gets
implicitly truncated as part of the open() (e.g. using O_TRUNC).

Notable special cases:
* open(..., O_RDONLY|O_TRUNC) can truncate files as well in Linux
* open() with O_TRUNC does *not* need the TRUNCATE right when it
creates a new file.

truncate(2) (on a path): requires the LANDLOCK_ACCESS_FS_TRUNCATE
right.

ftruncate(2) (on a file): requires that the file had the TRUNCATE
right when it was previously opened. File descriptors acquired by
other means than open(2) (e.g. memfd_create(2)) continue to support
truncation with ftruncate(2).

Cc: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Acked-by: Paul Moore <paul@paul-moore.com> (LSM)
Link: https://lore.kernel.org/r/20221018182216.301684-5-gnoack3000@gmail.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>

landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER

Add a new LANDLOCK_ACCESS_FS_REFER access right to enable policy writers
to allow sandboxed processes to link and rename files from and to a
specific set of file hierarchies. This access right should be composed
with LANDLOCK_ACCESS_FS_MAKE_* for the destination of a link or rename,
and with LANDLOCK_ACCESS_FS_REMOVE_* for a source of a rename. This
lift a Landlock limitation that always denied changing the parent of an
inode.

Renaming or linking to the same directory is still always allowed,
whatever LANDLOCK_ACCESS_FS_REFER is used or not, because it is not
considered a threat to user data.

However, creating multiple links or renaming to a different parent
directory may lead to privilege escalations if not handled properly.
Indeed, we must be sure that the source doesn't gain more privileges by
being accessible from the destination. This is handled by making sure
that the source hierarchy (including the referenced file or directory
itself) restricts at least as much the destination hierarchy. If it is
not the case, an EXDEV error is returned, making it potentially possible
for user space to copy the file hierarchy instead of moving or linking
it.

Instead of creating different access rights for the source and the
destination, we choose to make it simple and consistent for users.
Indeed, considering the previous constraint, it would be weird to
require such destination access right to be also granted to the source
(to make it a superset). Moreover, RENAME_EXCHANGE would also add to
the confusion because of paths being both a source and a destination.

See the provided documentation for additional details.

New tests are provided with a following commit.

Reviewed-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220506161102.525323-8-mic@digikod.net

selftests/landlock: Test landlock_create_ruleset(2) argument check ordering

Add inval_create_ruleset_arguments, extension of
inval_create_ruleset_flags, to also check error ordering for
landlock_create_ruleset(2).

This is similar to the previous commit checking landlock_add_rule(2).

Test coverage for security/landlock is 94.4% of 504 lines accorging to
gcc/gcov-11.

Link: https://lore.kernel.org/r/20220506160820.524344-11-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>

landlock: Change landlock_restrict_self(2) check ordering

According to the Landlock goal to be a security feature available to
unprivileges processes, it makes more sense to first check for
no_new_privs before checking anything else (i.e. syscall arguments).

Merge inval_fd_enforce and unpriv_enforce_without_no_new_privs tests
into the new restrict_self_checks_ordering. This is similar to the
previous commit checking other syscalls.

Link: https://lore.kernel.org/r/20220506160820.524344-10-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>

landlock: Change landlock_add_rule(2) argument check ordering

This makes more sense to first check the ruleset FD and then the rule
attribute. It will be useful to factor out code for other rule types.

Add inval_add_rule_arguments tests, extension of empty_path_beneath_attr
tests, to also check error ordering for landlock_add_rule(2).

Link: https://lore.kernel.org/r/20220506160820.524344-9-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>

selftests/landlock: Extend tests for minimal valid attribute size

This might be useful when the struct landlock_ruleset_attr will get more
fields.

Cc: Shuah Khan <shuah@kernel.org>
Link: https://lore.kernel.org/r/20220506160820.524344-4-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>

selftests/landlock: Format with clang-format

Let's follow a consistent and documented coding style. Everything may
not be to our liking but it is better than tacit knowledge. Moreover,
this will help maintain style consistency between different developers.

This contains only whitespace changes.

Automatically formatted with:
clang-format-14 -i tools/testing/selftests/landlock/*.[ch]

Link: https://lore.kernel.org/r/20220506160513.523257-6-mic@digikod.net
Cc: stable@vger.kernel.org
[mic: Update style according to
https://lore.kernel.org/r/02494cb8-2aa5-1769-f28d-d7206f284e5a@digikod.net]
Signed-off-by: Mickaël Salaün <mic@digikod.net>

landlock: Enable user space to infer supported features

Add a new flag LANDLOCK_CREATE_RULESET_VERSION to
landlock_create_ruleset(2). This enables to retreive a Landlock ABI
version that is useful to efficiently follow a best-effort security
approach. Indeed, it would be a missed opportunity to abort the whole
sandbox building, because some features are unavailable, instead of
protecting users as much as possible with the subset of features
provided by the running kernel.

This new flag enables user space to identify the minimum set of Landlock
features supported by the running kernel without relying on a filesystem
interface (e.g. /proc/version, which might be inaccessible) nor testing
multiple syscall argument combinations (i.e. syscall bisection). New
Landlock features will be documented and tied to a minimum version
number (greater than 1). The current version will be incremented for
each new kernel release supporting new Landlock features. User space
libraries can leverage this information to seamlessly restrict processes
as much as possible while being compatible with newer APIs.

This is a much more lighter approach than the previous
landlock_get_features(2): the complexity is pushed to user space
libraries. This flag meets similar needs as securityfs versions:
selinux/policyvers, apparmor/features/*/version* and tomoyo/version.

Supporting this flag now will be convenient for backward compatibility.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Link: https://lore.kernel.org/r/20210422154123.13086-14-mic@digikod.net
Signed-off-by: James Morris <jamorris@linux.microsoft.com>

selftests/landlock: Add user space tests

Test all Landlock system calls, ptrace hooks semantic and filesystem
access-control with multiple layouts.

Test coverage for security/landlock/ is 93.6% of lines. The code not
covered only deals with internal kernel errors (e.g. memory allocation)
and race conditions.

Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Reviewed-by: Vincent Dagonneau <vincent.dagonneau@ssi.gouv.fr>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210422154123.13086-11-mic@digikod.net
Signed-off-by: James Morris <jamorris@linux.microsoft.com>