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![Aristeu Rozanski](/assets/img/avatar_default.png)
This patch replaces the "whitelist" usage in the code and comments and replace them by exception list related information. Signed-off-by: Aristeu Rozanski <aris@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Cc: James Morris <jmorris@namei.org> Cc: Pavel Emelyanov <xemul@openvz.org> Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
593 lines
13 KiB
C
593 lines
13 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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/*
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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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bool deny_all;
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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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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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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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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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/**
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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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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(&ex->list);
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kfree(ex);
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}
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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_create(struct cgroup *cgroup)
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{
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struct dev_cgroup *dev_cgroup, *parent_dev_cgroup;
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struct cgroup *parent_cgroup;
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int ret;
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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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parent_cgroup = cgroup->parent;
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if (parent_cgroup == NULL)
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dev_cgroup->deny_all = false;
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else {
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parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
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mutex_lock(&devcgroup_mutex);
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ret = dev_exceptions_copy(&dev_cgroup->exceptions,
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&parent_dev_cgroup->exceptions);
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dev_cgroup->deny_all = parent_dev_cgroup->deny_all;
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mutex_unlock(&devcgroup_mutex);
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if (ret) {
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kfree(dev_cgroup);
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return ERR_PTR(ret);
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}
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}
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return &dev_cgroup->css;
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}
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static void devcgroup_destroy(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->deny_all == false) {
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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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*/
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static int may_access(struct dev_cgroup *dev_cgroup,
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struct dev_exception_item *refex)
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{
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struct dev_exception_item *ex;
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bool match = false;
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list_for_each_entry(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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/*
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* In two cases we'll consider this new exception valid:
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* - the dev cgroup has its default policy to allow + exception list:
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* the new exception should *not* match any of the exceptions
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* (!deny_all, !match)
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* - the dev cgroup has its default policy to deny + exception list:
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* the new exception *should* match the exceptions
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* (deny_all, match)
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*/
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if (dev_cgroup->deny_all == match)
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return 1;
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return 0;
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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);
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}
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/*
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* Modify the exception list using allow/deny rules.
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* CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
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* so we can give a container CAP_MKNOD to let it create devices but not
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* modify the exception list.
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* It seems likely we'll want to add a CAP_CONTAINER capability to allow
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* us to also grant CAP_SYS_ADMIN to containers without giving away the
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* device exception list controls, but for now we'll stick with CAP_SYS_ADMIN
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*
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* Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting
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* new access is only allowed if you're in the top-level cgroup, or your
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* parent cgroup has the access you're asking for.
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*/
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static int devcgroup_update_access(struct dev_cgroup *devcgroup,
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int filetype, const char *buffer)
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{
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const char *b;
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char *endp;
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int count;
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struct dev_exception_item ex;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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memset(&ex, 0, sizeof(ex));
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b = buffer;
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switch (*b) {
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case 'a':
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switch (filetype) {
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case DEVCG_ALLOW:
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if (!parent_has_perm(devcgroup, &ex))
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return -EPERM;
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dev_exception_clean(devcgroup);
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devcgroup->deny_all = false;
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break;
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case DEVCG_DENY:
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dev_exception_clean(devcgroup);
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devcgroup->deny_all = true;
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break;
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default:
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return -EINVAL;
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}
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return 0;
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case 'b':
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ex.type = DEV_BLOCK;
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break;
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case 'c':
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ex.type = DEV_CHAR;
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break;
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default:
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return -EINVAL;
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}
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b++;
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if (!isspace(*b))
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return -EINVAL;
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b++;
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if (*b == '*') {
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ex.major = ~0;
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b++;
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} else if (isdigit(*b)) {
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ex.major = simple_strtoul(b, &endp, 10);
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b = endp;
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} else {
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return -EINVAL;
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}
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if (*b != ':')
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return -EINVAL;
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b++;
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/* read minor */
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if (*b == '*') {
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ex.minor = ~0;
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b++;
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} else if (isdigit(*b)) {
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ex.minor = simple_strtoul(b, &endp, 10);
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b = endp;
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} else {
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return -EINVAL;
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}
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if (!isspace(*b))
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return -EINVAL;
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for (b++, count = 0; count < 3; count++, b++) {
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switch (*b) {
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case 'r':
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ex.access |= ACC_READ;
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break;
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case 'w':
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ex.access |= ACC_WRITE;
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break;
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case 'm':
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ex.access |= ACC_MKNOD;
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break;
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case '\n':
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case '\0':
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count = 3;
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break;
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default:
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return -EINVAL;
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}
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}
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switch (filetype) {
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case DEVCG_ALLOW:
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if (!parent_has_perm(devcgroup, &ex))
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return -EPERM;
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/*
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* If the default policy is to allow by default, try to remove
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* an matching exception instead. And be silent about it: we
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* don't want to break compatibility
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*/
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if (devcgroup->deny_all == false) {
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dev_exception_rm(devcgroup, &ex);
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return 0;
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}
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return dev_exception_add(devcgroup, &ex);
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case DEVCG_DENY:
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/*
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* If the default policy is to deny by default, try to remove
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* an matching exception instead. And be silent about it: we
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* don't want to break compatibility
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*/
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if (devcgroup->deny_all == true) {
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dev_exception_rm(devcgroup, &ex);
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return 0;
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}
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return dev_exception_add(devcgroup, &ex);
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default:
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return -EINVAL;
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}
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return 0;
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}
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static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
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const char *buffer)
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{
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int retval;
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mutex_lock(&devcgroup_mutex);
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retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
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cft->private, buffer);
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mutex_unlock(&devcgroup_mutex);
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return retval;
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}
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static struct cftype dev_cgroup_files[] = {
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{
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.name = "allow",
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.write_string = devcgroup_access_write,
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.private = DEVCG_ALLOW,
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},
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{
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.name = "deny",
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.write_string = devcgroup_access_write,
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.private = DEVCG_DENY,
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},
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{
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.name = "list",
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.read_seq_string = devcgroup_seq_read,
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.private = DEVCG_LIST,
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},
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{ } /* terminate */
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};
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struct cgroup_subsys devices_subsys = {
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.name = "devices",
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.can_attach = devcgroup_can_attach,
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.create = devcgroup_create,
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.destroy = devcgroup_destroy,
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.subsys_id = devices_subsys_id,
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.base_cftypes = dev_cgroup_files,
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/*
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* While devices cgroup has the rudimentary hierarchy support which
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* checks the parent's restriction, it doesn't properly propagates
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* config changes in ancestors to their descendents. A child
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* should only be allowed to add more restrictions to the parent's
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* configuration. Fix it and remove the following.
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*/
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.broken_hierarchy = true,
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};
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/**
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* __devcgroup_check_permission - checks if an inode operation is permitted
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* @dev_cgroup: the dev cgroup to be tested against
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* @type: device type
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* @major: device major number
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* @minor: device minor number
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* @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD
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*
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* returns 0 on success, -EPERM case the operation is not permitted
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*/
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static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
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short type, u32 major, u32 minor,
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short access)
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{
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struct dev_exception_item ex;
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int rc;
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memset(&ex, 0, sizeof(ex));
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ex.type = type;
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ex.major = major;
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ex.minor = minor;
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ex.access = access;
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rcu_read_lock();
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rc = may_access(dev_cgroup, &ex);
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rcu_read_unlock();
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if (!rc)
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return -EPERM;
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return 0;
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}
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|
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int __devcgroup_inode_permission(struct inode *inode, int mask)
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{
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struct dev_cgroup *dev_cgroup = task_devcgroup(current);
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short type, access = 0;
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|
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if (S_ISBLK(inode->i_mode))
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type = DEV_BLOCK;
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if (S_ISCHR(inode->i_mode))
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type = DEV_CHAR;
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if (mask & MAY_WRITE)
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access |= ACC_WRITE;
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if (mask & MAY_READ)
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access |= ACC_READ;
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|
|
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return __devcgroup_check_permission(dev_cgroup, type, imajor(inode),
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iminor(inode), access);
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}
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|
|
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int devcgroup_inode_mknod(int mode, dev_t dev)
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|
{
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struct dev_cgroup *dev_cgroup = task_devcgroup(current);
|
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short type;
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|
|
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if (!S_ISBLK(mode) && !S_ISCHR(mode))
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return 0;
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|
|
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if (S_ISBLK(mode))
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type = DEV_BLOCK;
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else
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type = DEV_CHAR;
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|
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return __devcgroup_check_permission(dev_cgroup, type, MAJOR(dev),
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|
MINOR(dev), ACC_MKNOD);
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|
|
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}
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