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![Mauro Carvalho Chehab](/assets/img/avatar_default.png)
Those files belong to the admin guide, so add them. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
826 lines
20 KiB
C
826 lines
20 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* device_cgroup.c - device cgroup subsystem
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*
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* Copyright 2007 IBM Corp
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*/
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#include <linux/device_cgroup.h>
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#include <linux/cgroup.h>
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#include <linux/ctype.h>
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#include <linux/list.h>
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#include <linux/uaccess.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include <linux/rcupdate.h>
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#include <linux/mutex.h>
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static DEFINE_MUTEX(devcgroup_mutex);
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enum devcg_behavior {
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DEVCG_DEFAULT_NONE,
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DEVCG_DEFAULT_ALLOW,
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DEVCG_DEFAULT_DENY,
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};
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/*
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* exception list locking rules:
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* hold devcgroup_mutex for update/read.
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* hold rcu_read_lock() for read.
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*/
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struct dev_exception_item {
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u32 major, minor;
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short type;
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short access;
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struct list_head list;
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struct rcu_head rcu;
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};
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struct dev_cgroup {
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struct cgroup_subsys_state css;
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struct list_head exceptions;
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enum devcg_behavior behavior;
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};
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static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
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{
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return s ? container_of(s, struct dev_cgroup, css) : NULL;
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}
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static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
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{
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return css_to_devcgroup(task_css(task, devices_cgrp_id));
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}
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/*
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* called under devcgroup_mutex
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*/
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static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig)
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{
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struct dev_exception_item *ex, *tmp, *new;
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lockdep_assert_held(&devcgroup_mutex);
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list_for_each_entry(ex, orig, list) {
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new = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
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if (!new)
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goto free_and_exit;
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list_add_tail(&new->list, dest);
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}
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return 0;
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free_and_exit:
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list_for_each_entry_safe(ex, tmp, dest, list) {
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list_del(&ex->list);
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kfree(ex);
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}
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return -ENOMEM;
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}
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/*
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* called under devcgroup_mutex
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*/
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static int dev_exception_add(struct dev_cgroup *dev_cgroup,
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struct dev_exception_item *ex)
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{
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struct dev_exception_item *excopy, *walk;
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lockdep_assert_held(&devcgroup_mutex);
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excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
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if (!excopy)
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return -ENOMEM;
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list_for_each_entry(walk, &dev_cgroup->exceptions, list) {
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if (walk->type != ex->type)
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continue;
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if (walk->major != ex->major)
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continue;
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if (walk->minor != ex->minor)
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continue;
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walk->access |= ex->access;
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kfree(excopy);
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excopy = NULL;
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}
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if (excopy != NULL)
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list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions);
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return 0;
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}
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/*
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* called under devcgroup_mutex
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*/
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static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
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struct dev_exception_item *ex)
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{
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struct dev_exception_item *walk, *tmp;
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lockdep_assert_held(&devcgroup_mutex);
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list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) {
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if (walk->type != ex->type)
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continue;
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if (walk->major != ex->major)
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continue;
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if (walk->minor != ex->minor)
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continue;
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walk->access &= ~ex->access;
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if (!walk->access) {
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list_del_rcu(&walk->list);
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kfree_rcu(walk, rcu);
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}
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}
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}
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static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
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{
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struct dev_exception_item *ex, *tmp;
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list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
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list_del_rcu(&ex->list);
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kfree_rcu(ex, rcu);
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}
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}
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/**
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* dev_exception_clean - frees all entries of the exception list
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* @dev_cgroup: dev_cgroup with the exception list to be cleaned
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*
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* called under devcgroup_mutex
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*/
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static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
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{
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lockdep_assert_held(&devcgroup_mutex);
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__dev_exception_clean(dev_cgroup);
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}
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static inline bool is_devcg_online(const struct dev_cgroup *devcg)
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{
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return (devcg->behavior != DEVCG_DEFAULT_NONE);
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}
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/**
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* devcgroup_online - initializes devcgroup's behavior and exceptions based on
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* parent's
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* @css: css getting online
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* returns 0 in case of success, error code otherwise
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*/
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static int devcgroup_online(struct cgroup_subsys_state *css)
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{
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struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
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struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent);
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int ret = 0;
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mutex_lock(&devcgroup_mutex);
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if (parent_dev_cgroup == NULL)
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dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
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else {
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ret = dev_exceptions_copy(&dev_cgroup->exceptions,
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&parent_dev_cgroup->exceptions);
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if (!ret)
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dev_cgroup->behavior = parent_dev_cgroup->behavior;
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}
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mutex_unlock(&devcgroup_mutex);
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return ret;
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}
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static void devcgroup_offline(struct cgroup_subsys_state *css)
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{
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struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
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mutex_lock(&devcgroup_mutex);
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dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
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mutex_unlock(&devcgroup_mutex);
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}
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/*
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* called from kernel/cgroup.c with cgroup_lock() held.
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*/
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static struct cgroup_subsys_state *
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devcgroup_css_alloc(struct cgroup_subsys_state *parent_css)
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{
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struct dev_cgroup *dev_cgroup;
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dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
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if (!dev_cgroup)
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return ERR_PTR(-ENOMEM);
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INIT_LIST_HEAD(&dev_cgroup->exceptions);
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dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
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return &dev_cgroup->css;
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}
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static void devcgroup_css_free(struct cgroup_subsys_state *css)
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{
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struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
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__dev_exception_clean(dev_cgroup);
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kfree(dev_cgroup);
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}
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#define DEVCG_ALLOW 1
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#define DEVCG_DENY 2
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#define DEVCG_LIST 3
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#define MAJMINLEN 13
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#define ACCLEN 4
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static void set_access(char *acc, short access)
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{
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int idx = 0;
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memset(acc, 0, ACCLEN);
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if (access & DEVCG_ACC_READ)
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acc[idx++] = 'r';
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if (access & DEVCG_ACC_WRITE)
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acc[idx++] = 'w';
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if (access & DEVCG_ACC_MKNOD)
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acc[idx++] = 'm';
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}
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static char type_to_char(short type)
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{
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if (type == DEVCG_DEV_ALL)
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return 'a';
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if (type == DEVCG_DEV_CHAR)
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return 'c';
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if (type == DEVCG_DEV_BLOCK)
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return 'b';
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return 'X';
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}
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static void set_majmin(char *str, unsigned m)
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{
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if (m == ~0)
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strcpy(str, "*");
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else
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sprintf(str, "%u", m);
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}
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static int devcgroup_seq_show(struct seq_file *m, void *v)
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{
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struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m));
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struct dev_exception_item *ex;
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char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
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rcu_read_lock();
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/*
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* To preserve the compatibility:
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* - Only show the "all devices" when the default policy is to allow
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* - List the exceptions in case the default policy is to deny
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* This way, the file remains as a "whitelist of devices"
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*/
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if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
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set_access(acc, DEVCG_ACC_MASK);
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set_majmin(maj, ~0);
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set_majmin(min, ~0);
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seq_printf(m, "%c %s:%s %s\n", type_to_char(DEVCG_DEV_ALL),
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maj, min, acc);
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} else {
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list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) {
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set_access(acc, ex->access);
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set_majmin(maj, ex->major);
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set_majmin(min, ex->minor);
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seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type),
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maj, min, acc);
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}
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}
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rcu_read_unlock();
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return 0;
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}
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/**
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* match_exception - iterates the exception list trying to find a complete match
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* @exceptions: list of exceptions
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* @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR)
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* @major: device file major number, ~0 to match all
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* @minor: device file minor number, ~0 to match all
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* @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD)
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*
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* It is considered a complete match if an exception is found that will
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* contain the entire range of provided parameters.
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*
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* Return: true in case it matches an exception completely
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*/
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static bool match_exception(struct list_head *exceptions, short type,
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u32 major, u32 minor, short access)
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{
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struct dev_exception_item *ex;
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list_for_each_entry_rcu(ex, exceptions, list) {
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if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK))
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continue;
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if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR))
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continue;
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if (ex->major != ~0 && ex->major != major)
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continue;
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if (ex->minor != ~0 && ex->minor != minor)
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continue;
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/* provided access cannot have more than the exception rule */
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if (access & (~ex->access))
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continue;
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return true;
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}
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return false;
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}
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/**
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* match_exception_partial - iterates the exception list trying to find a partial match
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* @exceptions: list of exceptions
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* @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR)
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* @major: device file major number, ~0 to match all
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* @minor: device file minor number, ~0 to match all
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* @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD)
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*
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* It is considered a partial match if an exception's range is found to
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* contain *any* of the devices specified by provided parameters. This is
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* used to make sure no extra access is being granted that is forbidden by
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* any of the exception list.
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*
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* Return: true in case the provided range mat matches an exception completely
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*/
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static bool match_exception_partial(struct list_head *exceptions, short type,
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u32 major, u32 minor, short access)
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{
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struct dev_exception_item *ex;
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list_for_each_entry_rcu(ex, exceptions, list) {
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if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK))
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continue;
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if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR))
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continue;
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/*
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* We must be sure that both the exception and the provided
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* range aren't masking all devices
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*/
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if (ex->major != ~0 && major != ~0 && ex->major != major)
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continue;
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if (ex->minor != ~0 && minor != ~0 && ex->minor != minor)
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continue;
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/*
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* In order to make sure the provided range isn't matching
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* an exception, all its access bits shouldn't match the
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* exception's access bits
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*/
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if (!(access & ex->access))
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continue;
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return true;
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}
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return false;
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}
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/**
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* verify_new_ex - verifies if a new exception is allowed by parent cgroup's permissions
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* @dev_cgroup: dev cgroup to be tested against
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* @refex: new exception
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* @behavior: behavior of the exception's dev_cgroup
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*
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* This is used to make sure a child cgroup won't have more privileges
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* than its parent
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*/
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static bool verify_new_ex(struct dev_cgroup *dev_cgroup,
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struct dev_exception_item *refex,
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enum devcg_behavior behavior)
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{
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bool match = false;
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RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
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!lockdep_is_held(&devcgroup_mutex),
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"device_cgroup:verify_new_ex called without proper synchronization");
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if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) {
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if (behavior == DEVCG_DEFAULT_ALLOW) {
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/*
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* new exception in the child doesn't matter, only
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* adding extra restrictions
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*/
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return true;
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} else {
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/*
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* new exception in the child will add more devices
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* that can be acessed, so it can't match any of
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* parent's exceptions, even slightly
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*/
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match = match_exception_partial(&dev_cgroup->exceptions,
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refex->type,
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refex->major,
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refex->minor,
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refex->access);
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if (match)
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return false;
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return true;
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}
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} else {
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/*
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* Only behavior == DEVCG_DEFAULT_DENY allowed here, therefore
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* the new exception will add access to more devices and must
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* be contained completely in an parent's exception to be
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* allowed
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*/
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match = match_exception(&dev_cgroup->exceptions, refex->type,
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refex->major, refex->minor,
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refex->access);
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if (match)
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/* parent has an exception that matches the proposed */
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return true;
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else
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return false;
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}
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return false;
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}
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/*
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* parent_has_perm:
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* when adding a new allow rule to a device exception list, the rule
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* must be allowed in the parent device
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*/
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static int parent_has_perm(struct dev_cgroup *childcg,
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struct dev_exception_item *ex)
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{
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struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent);
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if (!parent)
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return 1;
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return verify_new_ex(parent, ex, childcg->behavior);
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}
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/**
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* parent_allows_removal - verify if it's ok to remove an exception
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* @childcg: child cgroup from where the exception will be removed
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* @ex: exception being removed
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*
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* When removing an exception in cgroups with default ALLOW policy, it must
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* be checked if removing it will give the child cgroup more access than the
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* parent.
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*
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* Return: true if it's ok to remove exception, false otherwise
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*/
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static bool parent_allows_removal(struct dev_cgroup *childcg,
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struct dev_exception_item *ex)
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{
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struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent);
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if (!parent)
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return true;
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|
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/* It's always allowed to remove access to devices */
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if (childcg->behavior == DEVCG_DEFAULT_DENY)
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return true;
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/*
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* Make sure you're not removing part or a whole exception existing in
|
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* the parent cgroup
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*/
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return !match_exception_partial(&parent->exceptions, ex->type,
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ex->major, ex->minor, ex->access);
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}
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|
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/**
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* may_allow_all - checks if it's possible to change the behavior to
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* allow based on parent's rules.
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* @parent: device cgroup's parent
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* returns: != 0 in case it's allowed, 0 otherwise
|
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*/
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static inline int may_allow_all(struct dev_cgroup *parent)
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{
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if (!parent)
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return 1;
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return parent->behavior == DEVCG_DEFAULT_ALLOW;
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}
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|
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/**
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* revalidate_active_exceptions - walks through the active exception list and
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* revalidates the exceptions based on parent's
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* behavior and exceptions. The exceptions that
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* are no longer valid will be removed.
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* Called with devcgroup_mutex held.
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* @devcg: cgroup which exceptions will be checked
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*
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* This is one of the three key functions for hierarchy implementation.
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* This function is responsible for re-evaluating all the cgroup's active
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* exceptions due to a parent's exception change.
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* Refer to Documentation/admin-guide/cgroup-v1/devices.rst for more details.
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*/
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|
static void revalidate_active_exceptions(struct dev_cgroup *devcg)
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{
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struct dev_exception_item *ex;
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struct list_head *this, *tmp;
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|
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list_for_each_safe(this, tmp, &devcg->exceptions) {
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ex = container_of(this, struct dev_exception_item, list);
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if (!parent_has_perm(devcg, ex))
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dev_exception_rm(devcg, ex);
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}
|
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}
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|
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/**
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* propagate_exception - propagates a new exception to the children
|
|
* @devcg_root: device cgroup that added a new exception
|
|
* @ex: new exception to be propagated
|
|
*
|
|
* returns: 0 in case of success, != 0 in case of error
|
|
*/
|
|
static int propagate_exception(struct dev_cgroup *devcg_root,
|
|
struct dev_exception_item *ex)
|
|
{
|
|
struct cgroup_subsys_state *pos;
|
|
int rc = 0;
|
|
|
|
rcu_read_lock();
|
|
|
|
css_for_each_descendant_pre(pos, &devcg_root->css) {
|
|
struct dev_cgroup *devcg = css_to_devcgroup(pos);
|
|
|
|
/*
|
|
* Because devcgroup_mutex is held, no devcg will become
|
|
* online or offline during the tree walk (see on/offline
|
|
* methods), and online ones are safe to access outside RCU
|
|
* read lock without bumping refcnt.
|
|
*/
|
|
if (pos == &devcg_root->css || !is_devcg_online(devcg))
|
|
continue;
|
|
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* in case both root's behavior and devcg is allow, a new
|
|
* restriction means adding to the exception list
|
|
*/
|
|
if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW &&
|
|
devcg->behavior == DEVCG_DEFAULT_ALLOW) {
|
|
rc = dev_exception_add(devcg, ex);
|
|
if (rc)
|
|
return rc;
|
|
} else {
|
|
/*
|
|
* in the other possible cases:
|
|
* root's behavior: allow, devcg's: deny
|
|
* root's behavior: deny, devcg's: deny
|
|
* the exception will be removed
|
|
*/
|
|
dev_exception_rm(devcg, ex);
|
|
}
|
|
revalidate_active_exceptions(devcg);
|
|
|
|
rcu_read_lock();
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* Modify the exception list using allow/deny rules.
|
|
* CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
|
|
* so we can give a container CAP_MKNOD to let it create devices but not
|
|
* modify the exception list.
|
|
* It seems likely we'll want to add a CAP_CONTAINER capability to allow
|
|
* us to also grant CAP_SYS_ADMIN to containers without giving away the
|
|
* device exception list controls, but for now we'll stick with CAP_SYS_ADMIN
|
|
*
|
|
* Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting
|
|
* new access is only allowed if you're in the top-level cgroup, or your
|
|
* parent cgroup has the access you're asking for.
|
|
*/
|
|
static int devcgroup_update_access(struct dev_cgroup *devcgroup,
|
|
int filetype, char *buffer)
|
|
{
|
|
const char *b;
|
|
char temp[12]; /* 11 + 1 characters needed for a u32 */
|
|
int count, rc = 0;
|
|
struct dev_exception_item ex;
|
|
struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent);
|
|
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
|
|
memset(&ex, 0, sizeof(ex));
|
|
b = buffer;
|
|
|
|
switch (*b) {
|
|
case 'a':
|
|
switch (filetype) {
|
|
case DEVCG_ALLOW:
|
|
if (css_has_online_children(&devcgroup->css))
|
|
return -EINVAL;
|
|
|
|
if (!may_allow_all(parent))
|
|
return -EPERM;
|
|
dev_exception_clean(devcgroup);
|
|
devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
|
|
if (!parent)
|
|
break;
|
|
|
|
rc = dev_exceptions_copy(&devcgroup->exceptions,
|
|
&parent->exceptions);
|
|
if (rc)
|
|
return rc;
|
|
break;
|
|
case DEVCG_DENY:
|
|
if (css_has_online_children(&devcgroup->css))
|
|
return -EINVAL;
|
|
|
|
dev_exception_clean(devcgroup);
|
|
devcgroup->behavior = DEVCG_DEFAULT_DENY;
|
|
break;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
return 0;
|
|
case 'b':
|
|
ex.type = DEVCG_DEV_BLOCK;
|
|
break;
|
|
case 'c':
|
|
ex.type = DEVCG_DEV_CHAR;
|
|
break;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
b++;
|
|
if (!isspace(*b))
|
|
return -EINVAL;
|
|
b++;
|
|
if (*b == '*') {
|
|
ex.major = ~0;
|
|
b++;
|
|
} else if (isdigit(*b)) {
|
|
memset(temp, 0, sizeof(temp));
|
|
for (count = 0; count < sizeof(temp) - 1; count++) {
|
|
temp[count] = *b;
|
|
b++;
|
|
if (!isdigit(*b))
|
|
break;
|
|
}
|
|
rc = kstrtou32(temp, 10, &ex.major);
|
|
if (rc)
|
|
return -EINVAL;
|
|
} else {
|
|
return -EINVAL;
|
|
}
|
|
if (*b != ':')
|
|
return -EINVAL;
|
|
b++;
|
|
|
|
/* read minor */
|
|
if (*b == '*') {
|
|
ex.minor = ~0;
|
|
b++;
|
|
} else if (isdigit(*b)) {
|
|
memset(temp, 0, sizeof(temp));
|
|
for (count = 0; count < sizeof(temp) - 1; count++) {
|
|
temp[count] = *b;
|
|
b++;
|
|
if (!isdigit(*b))
|
|
break;
|
|
}
|
|
rc = kstrtou32(temp, 10, &ex.minor);
|
|
if (rc)
|
|
return -EINVAL;
|
|
} else {
|
|
return -EINVAL;
|
|
}
|
|
if (!isspace(*b))
|
|
return -EINVAL;
|
|
for (b++, count = 0; count < 3; count++, b++) {
|
|
switch (*b) {
|
|
case 'r':
|
|
ex.access |= DEVCG_ACC_READ;
|
|
break;
|
|
case 'w':
|
|
ex.access |= DEVCG_ACC_WRITE;
|
|
break;
|
|
case 'm':
|
|
ex.access |= DEVCG_ACC_MKNOD;
|
|
break;
|
|
case '\n':
|
|
case '\0':
|
|
count = 3;
|
|
break;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
switch (filetype) {
|
|
case DEVCG_ALLOW:
|
|
/*
|
|
* If the default policy is to allow by default, try to remove
|
|
* an matching exception instead. And be silent about it: we
|
|
* don't want to break compatibility
|
|
*/
|
|
if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
|
|
/* Check if the parent allows removing it first */
|
|
if (!parent_allows_removal(devcgroup, &ex))
|
|
return -EPERM;
|
|
dev_exception_rm(devcgroup, &ex);
|
|
break;
|
|
}
|
|
|
|
if (!parent_has_perm(devcgroup, &ex))
|
|
return -EPERM;
|
|
rc = dev_exception_add(devcgroup, &ex);
|
|
break;
|
|
case DEVCG_DENY:
|
|
/*
|
|
* If the default policy is to deny by default, try to remove
|
|
* an matching exception instead. And be silent about it: we
|
|
* don't want to break compatibility
|
|
*/
|
|
if (devcgroup->behavior == DEVCG_DEFAULT_DENY)
|
|
dev_exception_rm(devcgroup, &ex);
|
|
else
|
|
rc = dev_exception_add(devcgroup, &ex);
|
|
|
|
if (rc)
|
|
break;
|
|
/* we only propagate new restrictions */
|
|
rc = propagate_exception(devcgroup, &ex);
|
|
break;
|
|
default:
|
|
rc = -EINVAL;
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
static ssize_t devcgroup_access_write(struct kernfs_open_file *of,
|
|
char *buf, size_t nbytes, loff_t off)
|
|
{
|
|
int retval;
|
|
|
|
mutex_lock(&devcgroup_mutex);
|
|
retval = devcgroup_update_access(css_to_devcgroup(of_css(of)),
|
|
of_cft(of)->private, strstrip(buf));
|
|
mutex_unlock(&devcgroup_mutex);
|
|
return retval ?: nbytes;
|
|
}
|
|
|
|
static struct cftype dev_cgroup_files[] = {
|
|
{
|
|
.name = "allow",
|
|
.write = devcgroup_access_write,
|
|
.private = DEVCG_ALLOW,
|
|
},
|
|
{
|
|
.name = "deny",
|
|
.write = devcgroup_access_write,
|
|
.private = DEVCG_DENY,
|
|
},
|
|
{
|
|
.name = "list",
|
|
.seq_show = devcgroup_seq_show,
|
|
.private = DEVCG_LIST,
|
|
},
|
|
{ } /* terminate */
|
|
};
|
|
|
|
struct cgroup_subsys devices_cgrp_subsys = {
|
|
.css_alloc = devcgroup_css_alloc,
|
|
.css_free = devcgroup_css_free,
|
|
.css_online = devcgroup_online,
|
|
.css_offline = devcgroup_offline,
|
|
.legacy_cftypes = dev_cgroup_files,
|
|
};
|
|
|
|
/**
|
|
* __devcgroup_check_permission - checks if an inode operation is permitted
|
|
* @dev_cgroup: the dev cgroup to be tested against
|
|
* @type: device type
|
|
* @major: device major number
|
|
* @minor: device minor number
|
|
* @access: combination of DEVCG_ACC_WRITE, DEVCG_ACC_READ and DEVCG_ACC_MKNOD
|
|
*
|
|
* returns 0 on success, -EPERM case the operation is not permitted
|
|
*/
|
|
int __devcgroup_check_permission(short type, u32 major, u32 minor,
|
|
short access)
|
|
{
|
|
struct dev_cgroup *dev_cgroup;
|
|
bool rc;
|
|
|
|
rcu_read_lock();
|
|
dev_cgroup = task_devcgroup(current);
|
|
if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW)
|
|
/* Can't match any of the exceptions, even partially */
|
|
rc = !match_exception_partial(&dev_cgroup->exceptions,
|
|
type, major, minor, access);
|
|
else
|
|
/* Need to match completely one exception to be allowed */
|
|
rc = match_exception(&dev_cgroup->exceptions, type, major,
|
|
minor, access);
|
|
rcu_read_unlock();
|
|
|
|
if (!rc)
|
|
return -EPERM;
|
|
|
|
return 0;
|
|
}
|