The BUILD_BUG_ON check in domain_is_scoped() and
unmask_scoped_access() should check that the loop that counts down
client_layer finishes. We therefore check that the numbers
LANDLOCK_MAX_NUM_LAYERS-1 and -1 are both representable by that
integer. If they are representable, the numbers in between are
representable too, and the loop finishes.
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260327164838.38231-6-gnoack3000@gmail.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
The canonical kernel-doc form is "Return:" (singular, without trailing
"s"). Normalize all existing "Returns:" occurrences across the Landlock
source tree to the canonical form.
Also fix capitalization for consistency. Balance descriptions to
describe all possible returned values.
Consolidate bullet-point return descriptions into inline text for
functions with simple two-value or three-value returns for consistency.
Cc: Günther Noack <gnoack@google.com>
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260304193134.250495-3-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
The kernel-doc -Wreturn check warns about functions with documentation
comments that lack a "Return:" section. Add "Return:" documentation to
all functions missing it so that kernel-doc -Wreturn passes cleanly.
Convert existing function descriptions into a formal "Return:" section.
Also fix the inaccurate return documentation for
landlock_merge_ruleset() which claimed to return @parent directly, and
document the previously missing ERR_PTR() error return path. Document
the ABI version and errata return paths for landlock_create_ruleset()
which were previously only implied by the prose.
Cc: Günther Noack <gnoack@google.com>
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260304193134.250495-2-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Currently it is not obvious what "scoped" mean, and the fact that the
function returns true when access should be denied is slightly surprising
and in need of documentation.
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Signed-off-by: Tingmao Wang <m@maowtm.org>
Link: https://lore.kernel.org/r/06393bc18aee5bc278df5ef31c64a05b742ebc10.1766885035.git.m@maowtm.org
[mic: Fix formatting and improve consistency]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Add audit support for unix_stream_connect, unix_may_send, task_kill, and
file_send_sigiotask hooks.
The related blockers are:
- scope.abstract_unix_socket
- scope.signal
Audit event sample for abstract unix socket:
type=LANDLOCK_DENY msg=audit(1729738800.268:30): domain=195ba459b blockers=scope.abstract_unix_socket path=00666F6F
Audit event sample for signal:
type=LANDLOCK_DENY msg=audit(1729738800.291:31): domain=195ba459b blockers=scope.signal opid=1 ocomm="systemd"
Refactor and simplify error handling in LSM hooks.
Extend struct landlock_file_security with fown_layer and use it to log
the blocking domain. The struct aligned size is still 16 bytes.
Cc: Günther Noack <gnoack@google.com>
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-17-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Add a new AUDIT_LANDLOCK_ACCESS record type dedicated to an access
request denied by a Landlock domain. AUDIT_LANDLOCK_ACCESS indicates
that something unexpected happened.
For now, only denied access are logged, which means that any
AUDIT_LANDLOCK_ACCESS record is always followed by a SYSCALL record with
"success=no". However, log parsers should check this syscall property
because this is the only sign that a request was denied. Indeed, we
could have "success=yes" if Landlock would support a "permissive" mode.
We could also add a new field to AUDIT_LANDLOCK_DOMAIN for this mode
(see following commit).
By default, the only logged access requests are those coming from the
same executed program that enforced the Landlock restriction on itself.
In other words, no audit record are created for a task after it called
execve(2). This is required to avoid log spam because programs may only
be aware of their own restrictions, but not the inherited ones.
Following commits will allow to conditionally generate
AUDIT_LANDLOCK_ACCESS records according to dedicated
landlock_restrict_self(2)'s flags.
The AUDIT_LANDLOCK_ACCESS message contains:
- the "domain" ID restricting the action on an object,
- the "blockers" that are missing to allow the requested access,
- a set of fields identifying the related object (e.g. task identified
with "opid" and "ocomm").
The blockers are implicit restrictions (e.g. ptrace), or explicit access
rights (e.g. filesystem), or explicit scopes (e.g. signal). This field
contains a list of at least one element, each separated with a comma.
The initial blocker is "ptrace", which describe all implicit Landlock
restrictions related to ptrace (e.g. deny tracing of tasks outside a
sandbox).
Add audit support to ptrace_access_check and ptrace_traceme hooks. For
the ptrace_access_check case, we log the current/parent domain and the
child task. For the ptrace_traceme case, we log the parent domain and
the current/child task. Indeed, the requester and the target are the
current task, but the action would be performed by the parent task.
Audit event sample:
type=LANDLOCK_ACCESS msg=audit(1729738800.349:44): domain=195ba459b blockers=ptrace opid=1 ocomm="systemd"
type=SYSCALL msg=audit(1729738800.349:44): arch=c000003e syscall=101 success=no [...] pid=300 auid=0
A following commit adds user documentation.
Add KUnit tests to check reading of domain ID relative to layer level.
The quick return for non-landlocked tasks is moved from task_ptrace() to
each LSM hooks.
It is not useful to inline the audit_enabled check because other
computation are performed by landlock_log_denial().
Use scoped guards for RCU read-side critical sections.
Cc: Günther Noack <gnoack@google.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-10-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
This cosmetic change is needed for audit support, specifically to be
able to filter according to cross-execution boundaries.
struct landlock_file_security's size stay the same for now but it will
increase with struct landlock_cred_security's size.
Only save Landlock domain in hook_file_set_fowner() if the current
domain has LANDLOCK_SCOPE_SIGNAL, which was previously done for each
hook_file_send_sigiotask() calls. This should improve a bit
performance.
Replace hardcoded LANDLOCK_SCOPE_SIGNAL with the signal_scope.scope
variable.
Use scoped guards for RCU read-side critical sections.
Cc: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-8-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
This cosmetic change that is needed for audit support, specifically to
be able to filter according to cross-execution boundaries.
Replace hardcoded LANDLOCK_SCOPE_SIGNAL with the signal_scope.scope
variable.
Use scoped guards for RCU read-side critical sections.
Cc: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-7-mic@digikod.net
[mic: Update headers]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Create a new domain.h file containing the struct landlock_hierarchy
definition and helpers. This type will grow with audit support. This
also prepares for a new domain type.
Cc: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-4-mic@digikod.net
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Because Linux credentials are managed per thread, user space relies on
some hack to synchronize credential update across threads from the same
process. This is required by the Native POSIX Threads Library and
implemented by set*id(2) wrappers and libcap(3) to use tgkill(2) to
synchronize threads. See nptl(7) and libpsx(3). Furthermore, some
runtimes like Go do not enable developers to have control over threads
[1].
To avoid potential issues, and because threads are not security
boundaries, let's relax the Landlock (optional) signal scoping to always
allow signals sent between threads of the same process. This exception
is similar to the __ptrace_may_access() one.
hook_file_set_fowner() now checks if the target task is part of the same
process as the caller. If this is the case, then the related signal
triggered by the socket will always be allowed.
Scoping of abstract UNIX sockets is not changed because kernel objects
(e.g. sockets) should be tied to their creator's domain at creation
time.
Note that creating one Landlock domain per thread puts each of these
threads (and their future children) in their own scope, which is
probably not what users expect, especially in Go where we do not control
threads. However, being able to drop permissions on all threads should
not be restricted by signal scoping. We are working on a way to make it
possible to atomically restrict all threads of a process with the same
domain [2].
Add erratum for signal scoping.
Closes: https://github.com/landlock-lsm/go-landlock/issues/36
Fixes: 54a6e6bbf3 ("landlock: Add signal scoping")
Fixes: c899496501 ("selftests/landlock: Test signal scoping for threads")
Depends-on: 26f204380a ("fs: Fix file_set_fowner LSM hook inconsistencies")
Link: https://pkg.go.dev/kernel.org/pub/linux/libs/security/libcap/psx [1]
Link: https://github.com/landlock-lsm/linux/issues/2 [2]
Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Cc: stable@vger.kernel.org
Acked-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20250318161443.279194-6-mic@digikod.net
[mic: Add extra pointer check and RCU guard, and ease backport]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Do not walk through the domain hierarchy when the required scope is not
supported by this domain. This is the same approach as for filesystem
and network restrictions.
Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20241109110856.222842-4-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Currently, a sandbox process is not restricted to sending a signal (e.g.
SIGKILL) to a process outside the sandbox environment. The ability to
send a signal for a sandboxed process should be scoped the same way
abstract UNIX sockets are scoped. Therefore, we extend the "scoped"
field in a ruleset with LANDLOCK_SCOPE_SIGNAL to specify that a ruleset
will deny sending any signal from within a sandbox process to its parent
(i.e. any parent sandbox or non-sandboxed processes).
This patch adds file_set_fowner and file_free_security hooks to set and
release a pointer to the file owner's domain. This pointer, fown_domain
in landlock_file_security will be used in file_send_sigiotask to check
if the process can send a signal.
The ruleset_with_unknown_scope test is updated to support
LANDLOCK_SCOPE_SIGNAL.
This depends on two new changes:
- commit 1934b21261 ("file: reclaim 24 bytes from f_owner"): replace
container_of(fown, struct file, f_owner) with fown->file .
- commit 26f204380a ("fs: Fix file_set_fowner LSM hook
inconsistencies"): lock before calling the hook.
Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com>
Closes: https://github.com/landlock-lsm/linux/issues/8
Link: https://lore.kernel.org/r/df2b4f880a2ed3042992689a793ea0951f6798a5.1725657727.git.fahimitahera@gmail.com
[mic: Update landlock_get_current_domain()'s return type, improve and
fix locking in hook_file_set_fowner(), simplify and fix sleepable call
and locking issue in hook_file_send_sigiotask() and rebase on the latest
VFS tree, simplify hook_task_kill() and quickly return when not
sandboxed, improve comments, rename LANDLOCK_SCOPED_SIGNAL]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Introduce a new "scoped" member to landlock_ruleset_attr that can
specify LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET to restrict connection to
abstract UNIX sockets from a process outside of the socket's domain.
Two hooks are implemented to enforce these restrictions:
unix_stream_connect and unix_may_send.
Closes: https://github.com/landlock-lsm/linux/issues/7
Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com>
Link: https://lore.kernel.org/r/5f7ad85243b78427242275b93481cfc7c127764b.1725494372.git.fahimitahera@gmail.com
[mic: Fix commit message formatting, improve documentation, simplify
hook_unix_may_send(), and cosmetic fixes including rename of
LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
ptrace.[ch] are currently only used for the ptrace LSM hooks but their
scope will expand with IPCs and audit support. Rename ptrace.[ch] to
task.[ch], which better reflect their content. Similarly, rename
landlock_add_ptrace_hooks() to landlock_add_task_hooks(). Keep header
files for now.
Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20240307093923.1466071-2-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
