cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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ptrace.c (3244B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Landlock LSM - Ptrace hooks
      4 *
      5 * Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net>
      6 * Copyright © 2019-2020 ANSSI
      7 */
      8
      9#include <asm/current.h>
     10#include <linux/cred.h>
     11#include <linux/errno.h>
     12#include <linux/kernel.h>
     13#include <linux/lsm_hooks.h>
     14#include <linux/rcupdate.h>
     15#include <linux/sched.h>
     16
     17#include "common.h"
     18#include "cred.h"
     19#include "ptrace.h"
     20#include "ruleset.h"
     21#include "setup.h"
     22
     23/**
     24 * domain_scope_le - Checks domain ordering for scoped ptrace
     25 *
     26 * @parent: Parent domain.
     27 * @child: Potential child of @parent.
     28 *
     29 * Checks if the @parent domain is less or equal to (i.e. an ancestor, which
     30 * means a subset of) the @child domain.
     31 */
     32static bool domain_scope_le(const struct landlock_ruleset *const parent,
     33			    const struct landlock_ruleset *const child)
     34{
     35	const struct landlock_hierarchy *walker;
     36
     37	if (!parent)
     38		return true;
     39	if (!child)
     40		return false;
     41	for (walker = child->hierarchy; walker; walker = walker->parent) {
     42		if (walker == parent->hierarchy)
     43			/* @parent is in the scoped hierarchy of @child. */
     44			return true;
     45	}
     46	/* There is no relationship between @parent and @child. */
     47	return false;
     48}
     49
     50static bool task_is_scoped(const struct task_struct *const parent,
     51			   const struct task_struct *const child)
     52{
     53	bool is_scoped;
     54	const struct landlock_ruleset *dom_parent, *dom_child;
     55
     56	rcu_read_lock();
     57	dom_parent = landlock_get_task_domain(parent);
     58	dom_child = landlock_get_task_domain(child);
     59	is_scoped = domain_scope_le(dom_parent, dom_child);
     60	rcu_read_unlock();
     61	return is_scoped;
     62}
     63
     64static int task_ptrace(const struct task_struct *const parent,
     65		       const struct task_struct *const child)
     66{
     67	/* Quick return for non-landlocked tasks. */
     68	if (!landlocked(parent))
     69		return 0;
     70	if (task_is_scoped(parent, child))
     71		return 0;
     72	return -EPERM;
     73}
     74
     75/**
     76 * hook_ptrace_access_check - Determines whether the current process may access
     77 *			      another
     78 *
     79 * @child: Process to be accessed.
     80 * @mode: Mode of attachment.
     81 *
     82 * If the current task has Landlock rules, then the child must have at least
     83 * the same rules.  Else denied.
     84 *
     85 * Determines whether a process may access another, returning 0 if permission
     86 * granted, -errno if denied.
     87 */
     88static int hook_ptrace_access_check(struct task_struct *const child,
     89				    const unsigned int mode)
     90{
     91	return task_ptrace(current, child);
     92}
     93
     94/**
     95 * hook_ptrace_traceme - Determines whether another process may trace the
     96 *			 current one
     97 *
     98 * @parent: Task proposed to be the tracer.
     99 *
    100 * If the parent has Landlock rules, then the current task must have the same
    101 * or more rules.  Else denied.
    102 *
    103 * Determines whether the nominated task is permitted to trace the current
    104 * process, returning 0 if permission is granted, -errno if denied.
    105 */
    106static int hook_ptrace_traceme(struct task_struct *const parent)
    107{
    108	return task_ptrace(parent, current);
    109}
    110
    111static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
    112	LSM_HOOK_INIT(ptrace_access_check, hook_ptrace_access_check),
    113	LSM_HOOK_INIT(ptrace_traceme, hook_ptrace_traceme),
    114};
    115
    116__init void landlock_add_ptrace_hooks(void)
    117{
    118	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
    119			   LANDLOCK_NAME);
    120}