[PATCH v5 06/24] landlock: Prepare to use credential instead of domain for scope

Mickaël Salaün
2025-01-31T16:37:33Z

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>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20250131163059.1139617-7-mic@digikod.net
---

Changes since v4:
- New patch.
---
security/landlock/task.c | 50 +++++++++++++++++++++-------------------
1 file changed, 26 insertions(+), 24 deletions(-)

diff --git a/security/landlock/task.c b/security/landlock/task.c
index 98894ad1abc7..dbdfac11e015 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -7,6 +7,7 @@
*/

#include <asm/current.h>
+#include <linux/cleanup.h>
#include <linux/cred.h>
#include <linux/errno.h>
#include <linux/kernel.h>
@@ -213,15 +214,15 @@ static int hook_unix_stream_connect(struct sock *const sock,
struct sock *const other,
struct sock *const newsk)
{
- const struct landlock_ruleset *const dom =
- landlock_get_applicable_domain(landlock_get_current_domain(),
- unix_scope);
+ const struct landlock_cred_security *const subject =
+ landlock_get_applicable_subject(current_cred(), unix_scope,
+ NULL);

/* Quick return for non-landlocked tasks. */
- if (!dom)
+ if (!subject)
return 0;

- if (is_abstract_socket(other) && sock_is_scoped(other, dom))
+ if (is_abstract_socket(other) && sock_is_scoped(other, subject->domain))
return -EPERM;

return 0;
@@ -230,11 +231,11 @@ static int hook_unix_stream_connect(struct sock *const sock,
static int hook_unix_may_send(struct socket *const sock,
struct socket *const other)
{
- const struct landlock_ruleset *const dom =
- landlock_get_applicable_domain(landlock_get_current_domain(),
- unix_scope);
+ const struct landlock_cred_security *const subject =
+ landlock_get_applicable_subject(current_cred(), unix_scope,
+ NULL);

- if (!dom)
+ if (!subject)
return 0;

/*
@@ -244,7 +245,8 @@ static int hook_unix_may_send(struct socket *const sock,
if (unix_peer(sock->sk) == other->sk)
return 0;

- if (is_abstract_socket(other->sk) && sock_is_scoped(other->sk, dom))
+ if (is_abstract_socket(other->sk) &&
+ sock_is_scoped(other->sk, subject->domain))
return -EPERM;

return 0;
@@ -256,27 +258,27 @@ static const struct access_masks signal_scope = {

static int hook_task_kill(struct task_struct *const p,
struct kernel_siginfo *const info, const int sig,
- const struct cred *const cred)
+ const struct cred *cred)
{
bool is_scoped;
- const struct landlock_ruleset *dom;
+ const struct landlock_cred_security *subject;

- if (cred) {
- /* Dealing with USB IO. */
- dom = landlock_cred(cred)->domain;
- } else {
- dom = landlock_get_current_domain();
- }
- dom = landlock_get_applicable_domain(dom, signal_scope);
+ if (!cred)
+ /* Not dealing with USB IO. */
+ cred = current_cred();
+
+ subject = landlock_get_applicable_subject(cred, signal_scope, NULL);

/* Quick return for non-landlocked tasks. */
- if (!dom)
+ if (!subject)
return 0;

- rcu_read_lock();
- is_scoped = domain_is_scoped(dom, landlock_get_task_domain(p),
- LANDLOCK_SCOPE_SIGNAL);
- rcu_read_unlock();
+ scoped_guard(rcu)
+ {
+ is_scoped = domain_is_scoped(subject->domain,
+ landlock_get_task_domain(p),
+ signal_scope.scope);
+ }
if (is_scoped)
return -EPERM;

--
2.48.1