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![Rami Rosen](/assets/img/avatar_default.png)
In devcgroup_css_alloc(), there is no longer need for parent_cgroup. bd2953ebbb("devcg: propagate local changes down the hierarchy") made the variable parent_cgroup redundant. This patch removes parent_cgroup from devcgroup_css_alloc(). Signed-off-by: Rami Rosen <ramirose@gmail.com> Acked-by: Aristeu Rozanski <aris@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>
808 lines
19 KiB
C
808 lines
19 KiB
C
/*
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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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#define ACC_MKNOD 1
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#define ACC_READ 2
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#define ACC_WRITE 4
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#define ACC_MASK (ACC_MKNOD | ACC_READ | ACC_WRITE)
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#define DEV_BLOCK 1
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#define DEV_CHAR 2
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#define DEV_ALL 4 /* this represents all devices */
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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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/* temporary list for pending propagation operations */
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struct list_head propagate_pending;
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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 container_of(s, struct dev_cgroup, css);
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}
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static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup)
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{
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return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id));
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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_subsys_state(task, devices_subsys_id));
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}
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struct cgroup_subsys devices_subsys;
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static int devcgroup_can_attach(struct cgroup *new_cgrp,
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struct cgroup_taskset *set)
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{
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struct task_struct *task = cgroup_taskset_first(set);
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if (current != task && !capable(CAP_SYS_ADMIN))
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return -EPERM;
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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 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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* @cgroup: cgroup 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 *cgroup)
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{
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struct dev_cgroup *dev_cgroup, *parent_dev_cgroup = NULL;
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int ret = 0;
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mutex_lock(&devcgroup_mutex);
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dev_cgroup = cgroup_to_devcgroup(cgroup);
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if (cgroup->parent)
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parent_dev_cgroup = cgroup_to_devcgroup(cgroup->parent);
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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 *cgroup)
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{
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struct dev_cgroup *dev_cgroup = cgroup_to_devcgroup(cgroup);
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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 *devcgroup_css_alloc(struct cgroup *cgroup)
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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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INIT_LIST_HEAD(&dev_cgroup->propagate_pending);
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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 *cgroup)
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{
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struct dev_cgroup *dev_cgroup;
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dev_cgroup = cgroup_to_devcgroup(cgroup);
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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 & ACC_READ)
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acc[idx++] = 'r';
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if (access & ACC_WRITE)
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acc[idx++] = 'w';
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if (access & 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 == DEV_ALL)
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return 'a';
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if (type == DEV_CHAR)
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return 'c';
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if (type == 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_read(struct cgroup *cgroup, struct cftype *cft,
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struct seq_file *m)
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{
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struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
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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, 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(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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* may_access - verifies if a new exception is part of what is allowed
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* by a dev cgroup based on the default policy +
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* exceptions. This is used to make sure a child cgroup
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* won't have more privileges than its parent or to
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* verify if a certain access is allowed.
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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
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*/
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static bool may_access(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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struct dev_exception_item *ex;
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bool match = false;
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rcu_lockdep_assert(rcu_read_lock_held() ||
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lockdep_is_held(&devcgroup_mutex),
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"device_cgroup::may_access() called without proper synchronization");
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list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) {
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if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))
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continue;
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if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR))
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continue;
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if (ex->major != ~0 && ex->major != refex->major)
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continue;
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if (ex->minor != ~0 && ex->minor != refex->minor)
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continue;
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if (refex->access & (~ex->access))
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continue;
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match = true;
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break;
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}
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if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) {
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if (behavior == DEVCG_DEFAULT_ALLOW) {
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/* the exception will deny access to certain devices */
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return true;
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} else {
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/* the exception will allow access to certain devices */
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if (match)
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/*
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* a new exception allowing access shouldn't
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* match an parent's exception
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*/
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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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/* only behavior == DEVCG_DEFAULT_DENY allowed here */
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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 cgroup *pcg = childcg->css.cgroup->parent;
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struct dev_cgroup *parent;
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if (!pcg)
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return 1;
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parent = cgroup_to_devcgroup(pcg);
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return may_access(parent, ex, childcg->behavior);
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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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* 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/cgroups/devices.txt 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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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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* get_online_devcg - walks the cgroup tree and fills a list with the online
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* groups
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* @root: cgroup used as starting point
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* @online: list that will be filled with online groups
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*
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* Must be called with devcgroup_mutex held. Grabs RCU lock.
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* Because devcgroup_mutex is held, no devcg will become online or offline
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* during the tree walk (see devcgroup_online, devcgroup_offline)
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* A separated list is needed because propagate_behavior() and
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* propagate_exception() need to allocate memory and can block.
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*/
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static void get_online_devcg(struct cgroup *root, struct list_head *online)
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{
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struct cgroup *pos;
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struct dev_cgroup *devcg;
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lockdep_assert_held(&devcgroup_mutex);
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rcu_read_lock();
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cgroup_for_each_descendant_pre(pos, root) {
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devcg = cgroup_to_devcgroup(pos);
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if (is_devcg_online(devcg))
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list_add_tail(&devcg->propagate_pending, online);
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}
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rcu_read_unlock();
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}
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/**
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* propagate_exception - propagates a new exception to the children
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* @devcg_root: device cgroup that added a new exception
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* @ex: new exception to be propagated
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*
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* returns: 0 in case of success, != 0 in case of error
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*/
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static int propagate_exception(struct dev_cgroup *devcg_root,
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struct dev_exception_item *ex)
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{
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struct cgroup *root = devcg_root->css.cgroup;
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struct dev_cgroup *devcg, *parent, *tmp;
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int rc = 0;
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LIST_HEAD(pending);
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get_online_devcg(root, &pending);
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list_for_each_entry_safe(devcg, tmp, &pending, propagate_pending) {
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parent = cgroup_to_devcgroup(devcg->css.cgroup->parent);
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/*
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* in case both root's behavior and devcg is allow, a new
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* restriction means adding to the exception list
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*/
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if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW &&
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devcg->behavior == DEVCG_DEFAULT_ALLOW) {
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rc = dev_exception_add(devcg, ex);
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if (rc)
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break;
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} else {
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/*
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* in the other possible cases:
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* root's behavior: allow, devcg's: deny
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* root's behavior: deny, devcg's: deny
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* the exception will be removed
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*/
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dev_exception_rm(devcg, ex);
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}
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revalidate_active_exceptions(devcg);
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list_del_init(&devcg->propagate_pending);
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}
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return rc;
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}
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static inline bool has_children(struct dev_cgroup *devcgroup)
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{
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struct cgroup *cgrp = devcgroup->css.cgroup;
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return !list_empty(&cgrp->children);
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}
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/*
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* 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, const 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 cgroup *p = devcgroup->css.cgroup;
|
|
struct dev_cgroup *parent = NULL;
|
|
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
|
|
if (p->parent)
|
|
parent = cgroup_to_devcgroup(p->parent);
|
|
|
|
memset(&ex, 0, sizeof(ex));
|
|
b = buffer;
|
|
|
|
switch (*b) {
|
|
case 'a':
|
|
switch (filetype) {
|
|
case DEVCG_ALLOW:
|
|
if (has_children(devcgroup))
|
|
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 (has_children(devcgroup))
|
|
return -EINVAL;
|
|
|
|
dev_exception_clean(devcgroup);
|
|
devcgroup->behavior = DEVCG_DEFAULT_DENY;
|
|
break;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
return 0;
|
|
case 'b':
|
|
ex.type = DEV_BLOCK;
|
|
break;
|
|
case 'c':
|
|
ex.type = 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 |= ACC_READ;
|
|
break;
|
|
case 'w':
|
|
ex.access |= ACC_WRITE;
|
|
break;
|
|
case 'm':
|
|
ex.access |= ACC_MKNOD;
|
|
break;
|
|
case '\n':
|
|
case '\0':
|
|
count = 3;
|
|
break;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
switch (filetype) {
|
|
case DEVCG_ALLOW:
|
|
if (!parent_has_perm(devcgroup, &ex))
|
|
return -EPERM;
|
|
/*
|
|
* 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) {
|
|
dev_exception_rm(devcgroup, &ex);
|
|
return 0;
|
|
}
|
|
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 int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
|
|
const char *buffer)
|
|
{
|
|
int retval;
|
|
|
|
mutex_lock(&devcgroup_mutex);
|
|
retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
|
|
cft->private, buffer);
|
|
mutex_unlock(&devcgroup_mutex);
|
|
return retval;
|
|
}
|
|
|
|
static struct cftype dev_cgroup_files[] = {
|
|
{
|
|
.name = "allow",
|
|
.write_string = devcgroup_access_write,
|
|
.private = DEVCG_ALLOW,
|
|
},
|
|
{
|
|
.name = "deny",
|
|
.write_string = devcgroup_access_write,
|
|
.private = DEVCG_DENY,
|
|
},
|
|
{
|
|
.name = "list",
|
|
.read_seq_string = devcgroup_seq_read,
|
|
.private = DEVCG_LIST,
|
|
},
|
|
{ } /* terminate */
|
|
};
|
|
|
|
struct cgroup_subsys devices_subsys = {
|
|
.name = "devices",
|
|
.can_attach = devcgroup_can_attach,
|
|
.css_alloc = devcgroup_css_alloc,
|
|
.css_free = devcgroup_css_free,
|
|
.css_online = devcgroup_online,
|
|
.css_offline = devcgroup_offline,
|
|
.subsys_id = devices_subsys_id,
|
|
.base_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 ACC_WRITE, ACC_READ and ACC_MKNOD
|
|
*
|
|
* returns 0 on success, -EPERM case the operation is not permitted
|
|
*/
|
|
static int __devcgroup_check_permission(short type, u32 major, u32 minor,
|
|
short access)
|
|
{
|
|
struct dev_cgroup *dev_cgroup;
|
|
struct dev_exception_item ex;
|
|
int rc;
|
|
|
|
memset(&ex, 0, sizeof(ex));
|
|
ex.type = type;
|
|
ex.major = major;
|
|
ex.minor = minor;
|
|
ex.access = access;
|
|
|
|
rcu_read_lock();
|
|
dev_cgroup = task_devcgroup(current);
|
|
rc = may_access(dev_cgroup, &ex, dev_cgroup->behavior);
|
|
rcu_read_unlock();
|
|
|
|
if (!rc)
|
|
return -EPERM;
|
|
|
|
return 0;
|
|
}
|
|
|
|
int __devcgroup_inode_permission(struct inode *inode, int mask)
|
|
{
|
|
short type, access = 0;
|
|
|
|
if (S_ISBLK(inode->i_mode))
|
|
type = DEV_BLOCK;
|
|
if (S_ISCHR(inode->i_mode))
|
|
type = DEV_CHAR;
|
|
if (mask & MAY_WRITE)
|
|
access |= ACC_WRITE;
|
|
if (mask & MAY_READ)
|
|
access |= ACC_READ;
|
|
|
|
return __devcgroup_check_permission(type, imajor(inode), iminor(inode),
|
|
access);
|
|
}
|
|
|
|
int devcgroup_inode_mknod(int mode, dev_t dev)
|
|
{
|
|
short type;
|
|
|
|
if (!S_ISBLK(mode) && !S_ISCHR(mode))
|
|
return 0;
|
|
|
|
if (S_ISBLK(mode))
|
|
type = DEV_BLOCK;
|
|
else
|
|
type = DEV_CHAR;
|
|
|
|
return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev),
|
|
ACC_MKNOD);
|
|
|
|
}
|