path: root/security/device_cgroup.c

// SPDX-License-Identifier: GPL-2.0
/*
 * device_cgroup.c - device cgroup subsystem
 *
 * Copyright 2007 IBM Corp
 */

#include <linux/bpf-cgroup.h>
#include <linux/device_cgroup.h>
#include <linux/cgroup.h>
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/uaccess.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/rcupdate.h>
#include <linux/mutex.h>

#ifdef CONFIG_CGROUP_DEVICE

static DEFINE_MUTEX(devcgroup_mutex);

enum devcg_behavior {
	DEVCG_DEFAULT_NONE,
	DEVCG_DEFAULT_ALLOW,
	DEVCG_DEFAULT_DENY,
};

/*
 * exception list locking rules:
 * hold devcgroup_mutex for update/read.
 * hold rcu_read_lock() for read.
 */

struct dev_exception_item {
	u32 major, minor;
	short type;
	short access;
	struct list_head list;
	struct rcu_head rcu;
};

struct dev_cgroup {
	struct cgroup_subsys_state css;
	struct list_head exceptions;
	enum devcg_behavior behavior;
};

static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
{
	return s ? container_of(s, struct dev_cgroup, css) : NULL;
}

static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
{
	return css_to_devcgroup(task_css(task, devices_cgrp_id));
}

/*
 * called under devcgroup_mutex
 */
static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig)
{
	struct dev_exception_item *ex, *tmp, *new;

	lockdep_assert_held(&devcgroup_mutex);

	list_for_each_entry(ex, orig, list) {
		new = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
		if (!new)
			goto free_and_exit;
		list_add_tail(&new->list, dest);
	}

	return 0;

free_and_exit:
	list_for_each_entry_safe(ex, tmp, dest, list) {
		list_del(&ex->list);
		kfree(ex);
	}
	return -ENOMEM;
}

static void dev_exceptions_move(struct list_head *dest, struct list_head *orig)
{
	struct dev_exception_item *ex, *tmp;

	lockdep_assert_held(&devcgroup_mutex);

	list_for_each_entry_safe(ex, tmp, orig, list) {
		list_move_tail(&ex->list, dest);
	}
}

/*
 * called under devcgroup_mutex
 */
static int dev_exception_add(struct dev_cgroup *dev_cgroup,
			     struct dev_exception_item *ex)
{
	struct dev_exception_item *excopy, *walk;

	lockdep_assert_held(&devcgroup_mutex);

	excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
	if (!excopy)
		return -ENOMEM;

	list_for_each_entry(walk, &dev_cgroup->exceptions, list) {
		if (walk->type != ex->type)
			continue;
		if (walk->major != ex->major)
			continue;
		if (walk->minor != ex->minor)
			continue;

		walk->access |= ex->access;
		kfree(excopy);
		excopy = NULL;
	}

	if (excopy != NULL)
		list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions);
	return 0;
}

/*
 * called under devcgroup_mutex
 */
static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
			     struct dev_exception_item *ex)
{
	struct dev_exception_item *walk, *tmp;

	lockdep_assert_held(&devcgroup_mutex);

	list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) {
		if (walk->type != ex->type)
			continue;
		if (walk->major != ex->major)
			continue;
		if (walk->minor != ex->minor)
			continue;

		walk->access &= ~ex->access;
		if (!walk->access) {
			list_del_rcu(&walk->list);
			kfree_rcu(walk, rcu);
		}
	}
}

static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
{
	struct dev_exception_item *ex, *tmp;

	list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
		list_del_rcu(&ex->list);
		kfree_rcu(ex, rcu);
	}
}

/**
 * dev_exception_clean - frees all entries of the exception list
 * @dev_cgroup: dev_cgroup with the exception list to be cleaned
 *
 * called under devcgroup_mutex
 */
static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
{
	lockdep_assert_held(&devcgroup_mutex);

	__dev_exception_clean(dev_cgroup);
}

static inline bool is_devcg_online(const struct dev_cgroup *devcg)
{
	return (devcg->behavior != DEVCG_DEFAULT_NONE);
}

/**
 * devcgroup_online - initializes devcgroup's behavior and exceptions based on
 * 		      parent's
 * @css: css getting online
 * returns 0 in case of success, error code otherwise
 */
static int devcgroup_online(struct cgroup_subsys_state *css)
{
	struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
	struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent);
	int ret<