[PATCH v5 15/24] landlock: Log scoped denials

["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"

Cc: Günther Noack <gnoack@google.com>
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20250131163059.1139617-16-mic@digikod.net
---

Changes since v4:
- Rebase on top of the landlock_log_denial() and subject type changes.

Changes since v3:
- Cosmetic change to the "scope.*" blocker names.
- Extend commit message.

Changes since v1:
- New patch.
---
 security/landlock/audit.c |  8 +++++
 security/landlock/audit.h |  2 ++
 security/landlock/task.c  | 66 ++++++++++++++++++++++++++++++++++-----
 3 files changed, 69 insertions(+), 7 deletions(-)

diff --git a/security/landlock/audit.c b/security/landlock/audit.c
index 9c856b31f9f6..fc4d1dfb5c25 100644
--- a/security/landlock/audit.c
+++ b/security/landlock/audit.c
@@ -71,6 +71,14 @@ get_blocker(const enum landlock_request_type type,
 		if (WARN_ON_ONCE(access_bit >= ARRAY_SIZE(net_access_strings)))
 			return "unknown";
 		return net_access_strings[access_bit];
+
+	case LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET:
+		WARN_ON_ONCE(access_bit != -1);
+		return "scope.abstract_unix_socket";
+
+	case LANDLOCK_REQUEST_SCOPE_SIGNAL:
+		WARN_ON_ONCE(access_bit != -1);
+		return "scope.signal";
 	}
 
 	WARN_ON_ONCE(1);
diff --git a/security/landlock/audit.h b/security/landlock/audit.h
index eeff2c5bfa4f..aaf21b31baa8 100644
--- a/security/landlock/audit.h
+++ b/security/landlock/audit.h
@@ -20,6 +20,8 @@ enum landlock_request_type {
 	LANDLOCK_REQUEST_FS_CHANGE_LAYOUT,
 	LANDLOCK_REQUEST_FS_ACCESS,
 	LANDLOCK_REQUEST_NET_ACCESS,
+	LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET,
+	LANDLOCK_REQUEST_SCOPE_SIGNAL,
 };
 
 /*
diff --git a/security/landlock/task.c b/security/landlock/task.c
index 7b313a779de5..10bfba1994d0 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -264,16 +264,31 @@ static int hook_unix_stream_connect(struct sock *const sock,
 				    struct sock *const other,
 				    struct sock *const newsk)
 {
+	size_t handle_layer;
 	const struct landlock_cred_security *const subject =
 		landlock_get_applicable_subject(current_cred(), unix_scope,
-						NULL);
+						&handle_layer);
+	struct lsm_network_audit audit_net = {
+		.sk = other,
+	};
+	struct landlock_request request = {
+		.type = LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET,
+		.audit = {
+			.type = LSM_AUDIT_DATA_NET,
+			.u.net = &audit_net,
+		},
+	};
 
 	/* Quick return for non-landlocked tasks. */
 	if (!subject)
 		return 0;
 
-	if (is_abstract_socket(other) && sock_is_scoped(other, subject->domain))
+	if (is_abstract_socket(other) &&
+	    sock_is_scoped(other, subject->domain)) {
+		request.layer_plus_one = handle_layer + 1;
+		landlock_log_denial(subject, &request);
 		return -EPERM;
+	}
 
 	return 0;
 }
@@ -281,9 +296,20 @@ static int hook_unix_stream_connect(struct sock *const sock,
 static int hook_unix_may_send(struct socket *const sock,
 			      struct socket *const other)
 {
+	size_t handle_layer;
 	const struct landlock_cred_security *const subject =
 		landlock_get_applicable_subject(current_cred(), unix_scope,
-						NULL);
+						&handle_layer);
+	struct lsm_network_audit audit_net = {
+		.sk = other->sk,
+	};
+	struct landlock_request request = {
+		.type = LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET,
+		.audit = {
+			.type = LSM_AUDIT_DATA_NET,
+			.u.net = &audit_net,
+		},
+	};
 
 	if (!subject)
 		return 0;
@@ -296,8 +322,11 @@ static int hook_unix_may_send(struct socket *const sock,
 		return 0;
 
 	if (is_abstract_socket(other->sk) &&
-	    sock_is_scoped(other->sk, subject->domain))
+	    sock_is_scoped(other->sk, subject->domain)) {
+		request.layer_plus_one = handle_layer + 1;
+		landlock_log_denial(subject, &request);
 		return -EPERM;
+	}
 
 	return 0;
 }
@@ -311,13 +340,22 @@ static int hook_task_kill(struct task_struct *const p,
 			  const struct cred *cred)
 {
 	bool is_scoped;
+	size_t handle_layer;
 	const struct landlock_cred_security *subject;
+	struct landlock_request request = {
+		.type = LANDLOCK_REQUEST_SCOPE_SIGNAL,
+		.audit = {
+			.type = LSM_AUDIT_DATA_TASK,
+			.u.tsk = p,
+		},
+	};
 
 	if (!cred)
 		/* Not dealing with USB IO. */
 		cred = current_cred();
 
-	subject = landlock_get_applicable_subject(cred, signal_scope, NULL);
+	subject = landlock_get_applicable_subject(cred, signal_scope,
+						  &handle_layer);
 
 	/* Quick return for non-landlocked tasks. */
 	if (!subject)
@@ -329,8 +367,11 @@ static int hook_task_kill(struct task_struct *const p,
 					     landlock_get_task_domain(p),
 					     signal_scope.scope);
 	}
-	if (is_scoped)
+	if (is_scoped) {
+		request.layer_plus_one = handle_layer + 1;
+		landlock_log_denial(subject, &request);
 		return -EPERM;
+	}
 
 	return 0;
 }
@@ -338,7 +379,15 @@ static int hook_task_kill(struct task_struct *const p,
 static int hook_file_send_sigiotask(struct task_struct *tsk,
 				    struct fown_struct *fown, int signum)
 {
+	size_t handle_layer;
 	const struct landlock_cred_security *subject;
+	struct landlock_request request = {
+		.type = LANDLOCK_REQUEST_SCOPE_SIGNAL,
+		.audit = {
+			.type = LSM_AUDIT_DATA_TASK,
+			.u.tsk = tsk,
+		},
+	};
 	bool is_scoped = false;
 
 	/* Lock already held by send_sigio() and send_sigurg(). */
@@ -361,8 +410,11 @@ static int hook_file_send_sigiotask(struct task_struct *tsk,
 					     landlock_get_task_domain(tsk),
 					     signal_scope.scope);
 	}
-	if (is_scoped)
+	if (is_scoped) {
+		request.layer_plus_one = handle_layer + 1;
+		landlock_log_denial(subject, &request);
 		return -EPERM;
+	}
 
 	return 0;
 }
-- 
2.48.1