netif.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Network interface table.
  4 *
  5 * Network interfaces (devices) do not have a security field, so we
  6 * maintain a table associating each interface with a SID.
  7 *
  8 * Author: James Morris <jmorris@redhat.com>
  9 *
 10 * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
 11 * Copyright (C) 2007 Hewlett-Packard Development Company, L.P.
 12 *		      Paul Moore <paul@paul-moore.com>
 13 */
 14#include <linux/init.h>
 15#include <linux/types.h>
 16#include <linux/slab.h>
 17#include <linux/stddef.h>
 18#include <linux/kernel.h>
 19#include <linux/list.h>
 20#include <linux/notifier.h>
 21#include <linux/netdevice.h>
 22#include <linux/rcupdate.h>
 23#include <net/net_namespace.h>
 24
 25#include "initcalls.h"
 26#include "security.h"
 27#include "objsec.h"
 28#include "netif.h"
 29
 30#define SEL_NETIF_HASH_SIZE	64
 31#define SEL_NETIF_HASH_MAX	1024
 32
 33struct sel_netif {
 34	struct list_head list;
 35	struct netif_security_struct nsec;
 36	struct rcu_head rcu_head;
 37};
 38
 39static u32 sel_netif_total;
 40static DEFINE_SPINLOCK(sel_netif_lock);
 41static struct list_head sel_netif_hash[SEL_NETIF_HASH_SIZE];
 42
 43/**
 44 * sel_netif_hashfn - Hashing function for the interface table
 45 * @ns: the network namespace
 46 * @ifindex: the network interface
 47 *
 48 * Description:
 49 * This is the hashing function for the network interface table, it returns the
 50 * bucket number for the given interface.
 51 *
 52 */
 53static inline u32 sel_netif_hashfn(const struct net *ns, int ifindex)
 54{
 55	return (((uintptr_t)ns + ifindex) & (SEL_NETIF_HASH_SIZE - 1));
 56}
 57
 58/**
 59 * sel_netif_find - Search for an interface record
 60 * @ns: the network namespace
 61 * @ifindex: the network interface
 62 *
 63 * Description:
 64 * Search the network interface table and return the record matching @ifindex.
 65 * If an entry can not be found in the table return NULL.
 66 *
 67 */
 68static inline struct sel_netif *sel_netif_find(const struct net *ns,
 69					       int ifindex)
 70{
 71	u32 idx = sel_netif_hashfn(ns, ifindex);
 72	struct sel_netif *netif;
 73
 74	list_for_each_entry_rcu(netif, &sel_netif_hash[idx], list)
 75		if (net_eq(netif->nsec.ns, ns) &&
 76		    netif->nsec.ifindex == ifindex)
 77			return netif;
 78
 79	return NULL;
 80}
 81
 82/**
 83 * sel_netif_insert - Insert a new interface into the table
 84 * @netif: the new interface record
 85 *
 86 * Description:
 87 * Add a new interface record to the network interface hash table.  Returns
 88 * zero on success, negative values on failure.
 89 *
 90 */
 91static int sel_netif_insert(struct sel_netif *netif)
 92{
 93	u32 idx;
 94
 95	if (sel_netif_total >= SEL_NETIF_HASH_MAX)
 96		return -ENOSPC;
 97
 98	idx = sel_netif_hashfn(netif->nsec.ns, netif->nsec.ifindex);
 99	list_add_rcu(&netif->list, &sel_netif_hash[idx]);
100	sel_netif_total++;
101
102	return 0;
103}
104
105/**
106 * sel_netif_destroy - Remove an interface record from the table
107 * @netif: the existing interface record
108 *
109 * Description:
110 * Remove an existing interface record from the network interface table.
111 *
112 */
113static void sel_netif_destroy(struct sel_netif *netif)
114{
115	list_del_rcu(&netif->list);
116	sel_netif_total--;
117	kfree_rcu(netif, rcu_head);
118}
119
120/**
121 * sel_netif_sid_slow - Lookup the SID of a network interface using the policy
122 * @ns: the network namespace
123 * @ifindex: the network interface
124 * @sid: interface SID
125 *
126 * Description:
127 * This function determines the SID of a network interface by querying the
128 * security policy.  The result is added to the network interface table to
129 * speedup future queries.  Returns zero on success, negative values on
130 * failure.
131 *
132 */
133static int sel_netif_sid_slow(struct net *ns, int ifindex, u32 *sid)
134{
135	int ret = 0;
136	struct sel_netif *netif;
137	struct sel_netif *new;
138	struct net_device *dev;
139
140	/* NOTE: we always use init's network namespace since we don't
141	 * currently support containers */
142
143	dev = dev_get_by_index(ns, ifindex);
144	if (unlikely(dev == NULL)) {
145		pr_warn("SELinux: failure in %s(), invalid network interface (%d)\n",
146			__func__, ifindex);
147		return -ENOENT;
148	}
149
150	spin_lock_bh(&sel_netif_lock);
151	netif = sel_netif_find(ns, ifindex);
152	if (netif != NULL) {
153		*sid = netif->nsec.sid;
154		goto out;
155	}
156
157	ret = security_netif_sid(dev->name, sid);
158	if (ret != 0)
159		goto out;
160
161	/* If this memory allocation fails still return 0. The SID
162	 * is valid, it just won't be added to the cache.
163	 */
164	new = kmalloc(sizeof(*new), GFP_ATOMIC);
165	if (new) {
166		new->nsec.ns = ns;
167		new->nsec.ifindex = ifindex;
168		new->nsec.sid = *sid;
169		if (sel_netif_insert(new))
170			kfree(new);
171	}
172
173out:
174	spin_unlock_bh(&sel_netif_lock);
175	dev_put(dev);
176	if (unlikely(ret))
177		pr_warn("SELinux: failure in %s(), unable to determine network interface label (%d)\n",
178			__func__, ifindex);
179	return ret;
180}
181
182/**
183 * sel_netif_sid - Lookup the SID of a network interface
184 * @ns: the network namespace
185 * @ifindex: the network interface
186 * @sid: interface SID
187 *
188 * Description:
189 * This function determines the SID of a network interface using the fastest
190 * method possible.  First the interface table is queried, but if an entry
191 * can't be found then the policy is queried and the result is added to the
192 * table to speedup future queries.  Returns zero on success, negative values
193 * on failure.
194 *
195 */
196int sel_netif_sid(struct net *ns, int ifindex, u32 *sid)
197{
198	struct sel_netif *netif;
199
200	rcu_read_lock();
201	netif = sel_netif_find(ns, ifindex);
202	if (likely(netif != NULL)) {
203		*sid = netif->nsec.sid;
204		rcu_read_unlock();
205		return 0;
206	}
207	rcu_read_unlock();
208
209	return sel_netif_sid_slow(ns, ifindex, sid);
210}
211
212/**
213 * sel_netif_kill - Remove an entry from the network interface table
214 * @ns: the network namespace
215 * @ifindex: the network interface
216 *
217 * Description:
218 * This function removes the entry matching @ifindex from the network interface
219 * table if it exists.
220 *
221 */
222static void sel_netif_kill(const struct net *ns, int ifindex)
223{
224	struct sel_netif *netif;
225
226	rcu_read_lock();
227	spin_lock_bh(&sel_netif_lock);
228	netif = sel_netif_find(ns, ifindex);
229	if (netif)
230		sel_netif_destroy(netif);
231	spin_unlock_bh(&sel_netif_lock);
232	rcu_read_unlock();
233}
234
235/**
236 * sel_netif_flush - Flush the entire network interface table
237 *
238 * Description:
239 * Remove all entries from the network interface table.
240 *
241 */
242void sel_netif_flush(void)
243{
244	int idx;
245	struct sel_netif *netif;
246
247	spin_lock_bh(&sel_netif_lock);
248	for (idx = 0; idx < SEL_NETIF_HASH_SIZE; idx++)
249		list_for_each_entry(netif, &sel_netif_hash[idx], list)
250			sel_netif_destroy(netif);
251	spin_unlock_bh(&sel_netif_lock);
252}
253
254static int sel_netif_netdev_notifier_handler(struct notifier_block *this,
255					     unsigned long event, void *ptr)
256{
257	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
258
259	if (event == NETDEV_DOWN)
260		sel_netif_kill(dev_net(dev), dev->ifindex);
261
262	return NOTIFY_DONE;
263}
264
265static struct notifier_block sel_netif_netdev_notifier = {
266	.notifier_call = sel_netif_netdev_notifier_handler,
267};
268
269int __init sel_netif_init(void)
270{
271	int i;
272
273	if (!selinux_enabled_boot)
274		return 0;
275
276	for (i = 0; i < SEL_NETIF_HASH_SIZE; i++)
277		INIT_LIST_HEAD(&sel_netif_hash[i]);
278
279	register_netdevice_notifier(&sel_netif_netdev_notifier);
280
281	return 0;
282}
283