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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * Landlock LSM - Ptrace hooks
- *
- * Copyright © 2017-2020 Mickaël Salaün <[email protected]>
- * Copyright © 2019-2020 ANSSI
- */
- #include <asm/current.h>
- #include <linux/cred.h>
- #include <linux/errno.h>
- #include <linux/kernel.h>
- #include <linux/lsm_hooks.h>
- #include <linux/rcupdate.h>
- #include <linux/sched.h>
- #include "common.h"
- #include "cred.h"
- #include "ptrace.h"
- #include "ruleset.h"
- #include "setup.h"
- /**
- * domain_scope_le - Checks domain ordering for scoped ptrace
- *
- * @parent: Parent domain.
- * @child: Potential child of @parent.
- *
- * Checks if the @parent domain is less or equal to (i.e. an ancestor, which
- * means a subset of) the @child domain.
- */
- static bool domain_scope_le(const struct landlock_ruleset *const parent,
- const struct landlock_ruleset *const child)
- {
- const struct landlock_hierarchy *walker;
- if (!parent)
- return true;
- if (!child)
- return false;
- for (walker = child->hierarchy; walker; walker = walker->parent) {
- if (walker == parent->hierarchy)
- /* @parent is in the scoped hierarchy of @child. */
- return true;
- }
- /* There is no relationship between @parent and @child. */
- return false;
- }
- static bool task_is_scoped(const struct task_struct *const parent,
- const struct task_struct *const child)
- {
- bool is_scoped;
- const struct landlock_ruleset *dom_parent, *dom_child;
- rcu_read_lock();
- dom_parent = landlock_get_task_domain(parent);
- dom_child = landlock_get_task_domain(child);
- is_scoped = domain_scope_le(dom_parent, dom_child);
- rcu_read_unlock();
- return is_scoped;
- }
- static int task_ptrace(const struct task_struct *const parent,
- const struct task_struct *const child)
- {
- /* Quick return for non-landlocked tasks. */
- if (!landlocked(parent))
- return 0;
- if (task_is_scoped(parent, child))
- return 0;
- return -EPERM;
- }
- /**
- * hook_ptrace_access_check - Determines whether the current process may access
- * another
- *
- * @child: Process to be accessed.
- * @mode: Mode of attachment.
- *
- * If the current task has Landlock rules, then the child must have at least
- * the same rules. Else denied.
- *
- * Determines whether a process may access another, returning 0 if permission
- * granted, -errno if denied.
- */
- static int hook_ptrace_access_check(struct task_struct *const child,
- const unsigned int mode)
- {
- return task_ptrace(current, child);
- }
- /**
- * hook_ptrace_traceme - Determines whether another process may trace the
- * current one
- *
- * @parent: Task proposed to be the tracer.
- *
- * If the parent has Landlock rules, then the current task must have the same
- * or more rules. Else denied.
- *
- * Determines whether the nominated task is permitted to trace the current
- * process, returning 0 if permission is granted, -errno if denied.
- */
- static int hook_ptrace_traceme(struct task_struct *const parent)
- {
- return task_ptrace(parent, current);
- }
- static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
- LSM_HOOK_INIT(ptrace_access_check, hook_ptrace_access_check),
- LSM_HOOK_INIT(ptrace_traceme, hook_ptrace_traceme),
- };
- __init void landlock_add_ptrace_hooks(void)
- {
- security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
- LANDLOCK_NAME);
- }
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