1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Pkey table
  4 *
  5 * SELinux must keep a mapping of Infinband PKEYs to labels/SIDs.  This
  6 * mapping is maintained as part of the normal policy but a fast cache is
  7 * needed to reduce the lookup overhead.
  8 *
  9 * This code is heavily based on the "netif" and "netport" concept originally
 10 * developed by
 11 * James Morris <jmorris@redhat.com> and
 12 * Paul Moore <paul@paul-moore.com>
 13 *   (see security/selinux/netif.c and security/selinux/netport.c for more
 14 *   information)
 15 */
 16
 17/*
 18 * (c) Mellanox Technologies, 2016
 19 */
 20
 21#include <linux/types.h>
 22#include <linux/rcupdate.h>
 23#include <linux/list.h>
 24#include <linux/spinlock.h>
 25
 26#include "ibpkey.h"
 27#include "objsec.h"
 28
 29#define SEL_PKEY_HASH_SIZE       256
 30#define SEL_PKEY_HASH_BKT_LIMIT   16
 31
 32struct sel_ib_pkey_bkt {
 33	int size;
 34	struct list_head list;
 35};
 36
 37struct sel_ib_pkey {
 38	struct pkey_security_struct psec;
 39	struct list_head list;
 40	struct rcu_head rcu;
 41};
 42
 43static LIST_HEAD(sel_ib_pkey_list);
 44static DEFINE_SPINLOCK(sel_ib_pkey_lock);
 45static struct sel_ib_pkey_bkt sel_ib_pkey_hash[SEL_PKEY_HASH_SIZE];
 46
 47/**
 48 * sel_ib_pkey_hashfn - Hashing function for the pkey table
 49 * @pkey: pkey number
 50 *
 51 * Description:
 52 * This is the hashing function for the pkey table, it returns the bucket
 53 * number for the given pkey.
 54 *
 55 */
 56static unsigned int sel_ib_pkey_hashfn(u16 pkey)
 57{
 58	return (pkey & (SEL_PKEY_HASH_SIZE - 1));
 59}
 60
 61/**
 62 * sel_ib_pkey_find - Search for a pkey record
 63 * @subnet_prefix: subnet_prefix
 64 * @pkey_num: pkey_num
 65 *
 66 * Description:
 67 * Search the pkey table and return the matching record.  If an entry
 68 * can not be found in the table return NULL.
 69 *
 70 */
 71static struct sel_ib_pkey *sel_ib_pkey_find(u64 subnet_prefix, u16 pkey_num)
 72{
 73	unsigned int idx;
 74	struct sel_ib_pkey *pkey;
 75
 76	idx = sel_ib_pkey_hashfn(pkey_num);
 77	list_for_each_entry_rcu(pkey, &sel_ib_pkey_hash[idx].list, list) {
 78		if (pkey->psec.pkey == pkey_num &&
 79		    pkey->psec.subnet_prefix == subnet_prefix)
 80			return pkey;
 81	}
 82
 83	return NULL;
 84}
 85
 86/**
 87 * sel_ib_pkey_insert - Insert a new pkey into the table
 88 * @pkey: the new pkey record
 89 *
 90 * Description:
 91 * Add a new pkey record to the hash table.
 92 *
 93 */
 94static void sel_ib_pkey_insert(struct sel_ib_pkey *pkey)
 95{
 96	unsigned int idx;
 97
 98	/* we need to impose a limit on the growth of the hash table so check
 99	 * this bucket to make sure it is within the specified bounds
100	 */
101	idx = sel_ib_pkey_hashfn(pkey->psec.pkey);
102	list_add_rcu(&pkey->list, &sel_ib_pkey_hash[idx].list);
103	if (sel_ib_pkey_hash[idx].size == SEL_PKEY_HASH_BKT_LIMIT) {
104		struct sel_ib_pkey *tail;
105
106		tail = list_entry(
107			rcu_dereference_protected(
108				sel_ib_pkey_hash[idx].list.prev,
109				lockdep_is_held(&sel_ib_pkey_lock)),
110			struct sel_ib_pkey, list);
111		list_del_rcu(&tail->list);
112		kfree_rcu(tail, rcu);
113	} else {
114		sel_ib_pkey_hash[idx].size++;
115	}
116}
117
118/**
119 * sel_ib_pkey_sid_slow - Lookup the SID of a pkey using the policy
120 * @subnet_prefix: subnet prefix
121 * @pkey_num: pkey number
122 * @sid: pkey SID
123 *
124 * Description:
125 * This function determines the SID of a pkey by querying the security
126 * policy.  The result is added to the pkey table to speedup future
127 * queries.  Returns zero on success, negative values on failure.
128 *
129 */
130static int sel_ib_pkey_sid_slow(u64 subnet_prefix, u16 pkey_num, u32 *sid)
131{
132	int ret;
133	struct sel_ib_pkey *pkey;
134	struct sel_ib_pkey *new = NULL;
135	unsigned long flags;
136
137	spin_lock_irqsave(&sel_ib_pkey_lock, flags);
138	pkey = sel_ib_pkey_find(subnet_prefix, pkey_num);
139	if (pkey) {
140		*sid = pkey->psec.sid;
141		spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
142		return 0;
143	}
144
145	ret = security_ib_pkey_sid(&selinux_state, subnet_prefix, pkey_num,
146				   sid);
147	if (ret)
148		goto out;
149
150	/* If this memory allocation fails still return 0. The SID
151	 * is valid, it just won't be added to the cache.
152	 */
153	new = kzalloc(sizeof(*new), GFP_ATOMIC);
154	if (!new)
155		goto out;
156
157	new->psec.subnet_prefix = subnet_prefix;
158	new->psec.pkey = pkey_num;
159	new->psec.sid = *sid;
160	sel_ib_pkey_insert(new);
161
162out:
163	spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
164	return ret;
165}
166
167/**
168 * sel_ib_pkey_sid - Lookup the SID of a PKEY
169 * @subnet_prefix: subnet_prefix
170 * @pkey_num: pkey number
171 * @sid: pkey SID
172 *
173 * Description:
174 * This function determines the SID of a PKEY using the fastest method
175 * possible.  First the pkey table is queried, but if an entry can't be found
176 * then the policy is queried and the result is added to the table to speedup
177 * future queries.  Returns zero on success, negative values on failure.
178 *
179 */
180int sel_ib_pkey_sid(u64 subnet_prefix, u16 pkey_num, u32 *sid)
181{
182	struct sel_ib_pkey *pkey;
183
184	rcu_read_lock();
185	pkey = sel_ib_pkey_find(subnet_prefix, pkey_num);
186	if (pkey) {
187		*sid = pkey->psec.sid;
188		rcu_read_unlock();
189		return 0;
190	}
191	rcu_read_unlock();
192
193	return sel_ib_pkey_sid_slow(subnet_prefix, pkey_num, sid);
194}
195
196/**
197 * sel_ib_pkey_flush - Flush the entire pkey table
198 *
199 * Description:
200 * Remove all entries from the pkey table
201 *
202 */
203void sel_ib_pkey_flush(void)
204{
205	unsigned int idx;
206	struct sel_ib_pkey *pkey, *pkey_tmp;
207	unsigned long flags;
208
209	spin_lock_irqsave(&sel_ib_pkey_lock, flags);
210	for (idx = 0; idx < SEL_PKEY_HASH_SIZE; idx++) {
211		list_for_each_entry_safe(pkey, pkey_tmp,
212					 &sel_ib_pkey_hash[idx].list, list) {
213			list_del_rcu(&pkey->list);
214			kfree_rcu(pkey, rcu);
215		}
216		sel_ib_pkey_hash[idx].size = 0;
217	}
218	spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
219}
220
221static __init int sel_ib_pkey_init(void)
222{
223	int iter;
224
225	if (!selinux_enabled)
226		return 0;
227
228	for (iter = 0; iter < SEL_PKEY_HASH_SIZE; iter++) {
229		INIT_LIST_HEAD(&sel_ib_pkey_hash[iter].list);
230		sel_ib_pkey_hash[iter].size = 0;
231	}
232
233	return 0;
234}
235
236subsys_initcall(sel_ib_pkey_init);