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 <gno...@google.com>
Signed-off-by: Mickaël Salaün <m...@digikod.net>
---
Changes since v6:
- Refactor and simplify hook_file_set_fowner().
- Rebase on the signal scope fix.
Changes since v5:
- Only call landlock_get_ruleset() when needed in
hook_file_set_fowner().
Changes since v4:
- New patch.
---
security/landlock/fs.c | 20 ++++++++++++++------
security/landlock/fs.h | 12 +++++++-----
security/landlock/task.c | 25 ++++++++++++++++---------
3 files changed, 37 insertions(+), 20 deletions(-)
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index fd858f989a3d..13d1cd78e8c8 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -1644,9 +1644,9 @@ static int hook_file_ioctl_compat(struct file *file,
unsigned int cmd,
static void hook_file_set_fowner(struct file *file)
{
struct fown_struct *fown = file_f_owner(file);
- struct landlock_ruleset *new_dom = NULL;
struct landlock_ruleset *prev_dom;
struct task_struct *p;
+ struct landlock_cred_security fown_subject = {};
/*
* Lock already held by __f_setown(), see commit 26f204380a3c ("fs: Fix
@@ -1660,12 +1660,20 @@ static void hook_file_set_fowner(struct file *file)
*/
p = pid_task(fown->pid, fown->pid_type);
if (!same_thread_group(p, current)) {
- new_dom = landlock_get_current_domain();
- landlock_get_ruleset(new_dom);
+ static const struct access_masks signal_scope = {
+ .scope = LANDLOCK_SCOPE_SIGNAL,
+ };
+ const struct landlock_cred_security *new_subject =
+ landlock_get_applicable_subject(current_cred(),
+ signal_scope, NULL);
+ if (new_subject) {
+ landlock_get_ruleset(new_subject->domain);
+ fown_subject = *new_subject;
+ }
}
- prev_dom = landlock_file(file)->fown_domain;
- landlock_file(file)->fown_domain = new_dom;
+ prev_dom = landlock_file(file)->fown_subject.domain;
+ landlock_file(file)->fown_subject = fown_subject;
/* Called in an RCU read-side critical section. */
landlock_put_ruleset_deferred(prev_dom);
@@ -1673,7 +1681,7 @@ static void hook_file_set_fowner(struct file *file)
static void hook_file_free_security(struct file *file)
{
- landlock_put_ruleset_deferred(landlock_file(file)->fown_domain);
+ landlock_put_ruleset_deferred(landlock_file(file)->fown_subject.domain);
}
static struct security_hook_list landlock_hooks[] __ro_after_init = {
diff --git a/security/landlock/fs.h b/security/landlock/fs.h
index d445f411c26a..1449a90e92c7 100644
--- a/security/landlock/fs.h
+++ b/security/landlock/fs.h
@@ -14,6 +14,7 @@
#include <linux/rcupdate.h>
#include "access.h"
+#include "cred.h"
#include "ruleset.h"
#include "setup.h"
@@ -54,12 +55,13 @@ struct landlock_file_security {
*/
access_mask_t allowed_access;
/**
- * @fown_domain: Domain of the task that set the PID that may receive a
- * signal e.g., SIGURG when writing MSG_OOB to the related socket.
- * This pointer is protected by the related file->f_owner->lock, as for
- * fown_struct's members: pid, uid, and euid.
+ * @fown_subject: Landlock credential of the task that set the PID that
+ * may receive a signal e.g., SIGURG when writing MSG_OOB to the
+ * related socket. This pointer is protected by the related
+ * file->f_owner->lock, as for fown_struct's members: pid, uid, and
+ * euid.
*/
- struct landlock_ruleset *fown_domain;
+ struct landlock_cred_security fown_subject;
};
/**
diff --git a/security/landlock/task.c b/security/landlock/task.c
index a44b8e4a6ea6..1ccd780e1354 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -301,22 +301,29 @@ 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)
{
- const struct landlock_ruleset *dom;
+ const struct landlock_cred_security *subject;
bool is_scoped = false;
/* Lock already held by send_sigio() and send_sigurg(). */
lockdep_assert_held(&fown->lock);
- dom = landlock_get_applicable_domain(
- landlock_file(fown->file)->fown_domain, signal_scope);
+ subject = &landlock_file(fown->file)->fown_subject;
- /* Quick return for unowned socket. */
- if (!dom)
+ /*
+ * Quick return for unowned socket.
+ *
+ * subject->domain has already been filtered when saved by
+ * hook_file_set_fowner(), so there is no need to call
+ * landlock_get_applicable_subject() here.
+ */
+ if (!subject->domain)
return 0;
- rcu_read_lock();
- is_scoped = domain_is_scoped(dom, landlock_get_task_domain(tsk),
- LANDLOCK_SCOPE_SIGNAL);
- rcu_read_unlock();
+ scoped_guard(rcu)
+ {
+ is_scoped = domain_is_scoped(subject->domain,
+ landlock_get_task_domain(tsk),
+ signal_scope.scope);
+ }
if (is_scoped)
return -EPERM;
--
2.49.0
