1/*
  2 * Pkey table
  3 *
  4 * SELinux must keep a mapping of Infinband PKEYs to labels/SIDs.  This
  5 * mapping is maintained as part of the normal policy but a fast cache is
  6 * needed to reduce the lookup overhead.
  7 *
  8 * This code is heavily based on the "netif" and "netport" concept originally
  9 * developed by
 10 * James Morris <jmorris@redhat.com> and
 11 * Paul Moore <paul@paul-moore.com>
 12 *   (see security/selinux/netif.c and security/selinux/netport.c for more
 13 *   information)
 14 *
 15 */
 16
 17/*
 18 * (c) Mellanox Technologies, 2016
 19 *
 20 * This program is free software: you can redistribute it and/or modify
 21 * it under the terms of version 2 of the GNU General Public License as
 22 * published by the Free Software Foundation.
 23 *
 24 * This program is distributed in the hope that it will be useful,
 25 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 26 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 27 * GNU General Public License for more details.
 28 *
 29 */
 30
 31#include <linux/types.h>
 32#include <linux/rcupdate.h>
 33#include <linux/list.h>
 34#include <linux/spinlock.h>
 35
 36#include "ibpkey.h"
 37#include "objsec.h"
 38
 39#define SEL_PKEY_HASH_SIZE       256
 40#define SEL_PKEY_HASH_BKT_LIMIT   16
 41
 42struct sel_ib_pkey_bkt {
 43	int size;
 44	struct list_head list;
 45};
 46
 47struct sel_ib_pkey {
 48	struct pkey_security_struct psec;
 49	struct list_head list;
 50	struct rcu_head rcu;
 51};
 52
 53static LIST_HEAD(sel_ib_pkey_list);
 54static DEFINE_SPINLOCK(sel_ib_pkey_lock);
 55static struct sel_ib_pkey_bkt sel_ib_pkey_hash[SEL_PKEY_HASH_SIZE];
 56
 57/**
 58 * sel_ib_pkey_hashfn - Hashing function for the pkey table
 59 * @pkey: pkey number
 60 *
 61 * Description:
 62 * This is the hashing function for the pkey table, it returns the bucket
 63 * number for the given pkey.
 64 *
 65 */
 66static unsigned int sel_ib_pkey_hashfn(u16 pkey)
 67{
 68	return (pkey & (SEL_PKEY_HASH_SIZE - 1));
 69}
 70
 71/**
 72 * sel_ib_pkey_find - Search for a pkey record
 73 * @subnet_prefix: subnet_prefix
 74 * @pkey_num: pkey_num
 75 *
 76 * Description:
 77 * Search the pkey table and return the matching record.  If an entry
 78 * can not be found in the table return NULL.
 79 *
 80 */
 81static struct sel_ib_pkey *sel_ib_pkey_find(u64 subnet_prefix, u16 pkey_num)
 82{
 83	unsigned int idx;
 84	struct sel_ib_pkey *pkey;
 85
 86	idx = sel_ib_pkey_hashfn(pkey_num);
 87	list_for_each_entry_rcu(pkey, &sel_ib_pkey_hash[idx].list, list) {
 88		if (pkey->psec.pkey == pkey_num &&
 89		    pkey->psec.subnet_prefix == subnet_prefix)
 90			return pkey;
 91	}
 92
 93	return NULL;
 94}
 95
 96/**
 97 * sel_ib_pkey_insert - Insert a new pkey into the table
 98 * @pkey: the new pkey record
 99 *
100 * Description:
101 * Add a new pkey record to the hash table.
102 *
103 */
104static void sel_ib_pkey_insert(struct sel_ib_pkey *pkey)
105{
106	unsigned int idx;
107
108	/* we need to impose a limit on the growth of the hash table so check
109	 * this bucket to make sure it is within the specified bounds
110	 */
111	idx = sel_ib_pkey_hashfn(pkey->psec.pkey);
112	list_add_rcu(&pkey->list, &sel_ib_pkey_hash[idx].list);
113	if (sel_ib_pkey_hash[idx].size == SEL_PKEY_HASH_BKT_LIMIT) {
114		struct sel_ib_pkey *tail;
115
116		tail = list_entry(
117			rcu_dereference_protected(
118				sel_ib_pkey_hash[idx].list.prev,
119				lockdep_is_held(&sel_ib_pkey_lock)),
120			struct sel_ib_pkey, list);
121		list_del_rcu(&tail->list);
122		kfree_rcu(tail, rcu);
123	} else {
124		sel_ib_pkey_hash[idx].size++;
125	}
126}
127
128/**
129 * sel_ib_pkey_sid_slow - Lookup the SID of a pkey using the policy
130 * @subnet_prefix: subnet prefix
131 * @pkey_num: pkey number
132 * @sid: pkey SID
133 *
134 * Description:
135 * This function determines the SID of a pkey by querying the security
136 * policy.  The result is added to the pkey table to speedup future
137 * queries.  Returns zero on success, negative values on failure.
138 *
139 */
140static int sel_ib_pkey_sid_slow(u64 subnet_prefix, u16 pkey_num, u32 *sid)
141{
142	int ret;
143	struct sel_ib_pkey *pkey;
144	struct sel_ib_pkey *new = NULL;
145	unsigned long flags;
146
147	spin_lock_irqsave(&sel_ib_pkey_lock, flags);
148	pkey = sel_ib_pkey_find(subnet_prefix, pkey_num);
149	if (pkey) {
150		*sid = pkey->psec.sid;
151		spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
152		return 0;
153	}
154
155	ret = security_ib_pkey_sid(&selinux_state, subnet_prefix, pkey_num,
156				   sid);
157	if (ret)
158		goto out;
159
160	/* If this memory allocation fails still return 0. The SID
161	 * is valid, it just won't be added to the cache.
162	 */
163	new = kzalloc(sizeof(*new), GFP_ATOMIC);
164	if (!new)
165		goto out;
166
167	new->psec.subnet_prefix = subnet_prefix;
168	new->psec.pkey = pkey_num;
169	new->psec.sid = *sid;
170	sel_ib_pkey_insert(new);
171
172out:
173	spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
174	return ret;
175}
176
177/**
178 * sel_ib_pkey_sid - Lookup the SID of a PKEY
179 * @subnet_prefix: subnet_prefix
180 * @pkey_num: pkey number
181 * @sid: pkey SID
182 *
183 * Description:
184 * This function determines the SID of a PKEY using the fastest method
185 * possible.  First the pkey table is queried, but if an entry can't be found
186 * then the policy is queried and the result is added to the table to speedup
187 * future queries.  Returns zero on success, negative values on failure.
188 *
189 */
190int sel_ib_pkey_sid(u64 subnet_prefix, u16 pkey_num, u32 *sid)
191{
192	struct sel_ib_pkey *pkey;
193
194	rcu_read_lock();
195	pkey = sel_ib_pkey_find(subnet_prefix, pkey_num);
196	if (pkey) {
197		*sid = pkey->psec.sid;
198		rcu_read_unlock();
199		return 0;
200	}
201	rcu_read_unlock();
202
203	return sel_ib_pkey_sid_slow(subnet_prefix, pkey_num, sid);
204}
205
206/**
207 * sel_ib_pkey_flush - Flush the entire pkey table
208 *
209 * Description:
210 * Remove all entries from the pkey table
211 *
212 */
213void sel_ib_pkey_flush(void)
214{
215	unsigned int idx;
216	struct sel_ib_pkey *pkey, *pkey_tmp;
217	unsigned long flags;
218
219	spin_lock_irqsave(&sel_ib_pkey_lock, flags);
220	for (idx = 0; idx < SEL_PKEY_HASH_SIZE; idx++) {
221		list_for_each_entry_safe(pkey, pkey_tmp,
222					 &sel_ib_pkey_hash[idx].list, list) {
223			list_del_rcu(&pkey->list);
224			kfree_rcu(pkey, rcu);
225		}
226		sel_ib_pkey_hash[idx].size = 0;
227	}
228	spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
229}
230
231static __init int sel_ib_pkey_init(void)
232{
233	int iter;
234
235	if (!selinux_enabled)
236		return 0;
237
238	for (iter = 0; iter < SEL_PKEY_HASH_SIZE; iter++) {
239		INIT_LIST_HEAD(&sel_ib_pkey_hash[iter].list);
240		sel_ib_pkey_hash[iter].size = 0;
241	}
242
243	return 0;
244}
245
246subsys_initcall(sel_ib_pkey_init);