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 DEFINE_SPINLOCK(sel_ib_pkey_lock);
 44static struct sel_ib_pkey_bkt sel_ib_pkey_hash[SEL_PKEY_HASH_SIZE];
 45
 46/**
 47 * sel_ib_pkey_hashfn - Hashing function for the pkey table
 48 * @pkey: pkey number
 49 *
 50 * Description:
 51 * This is the hashing function for the pkey table, it returns the bucket
 52 * number for the given pkey.
 53 *
 54 */
 55static unsigned int sel_ib_pkey_hashfn(u16 pkey)
 56{
 57	return (pkey & (SEL_PKEY_HASH_SIZE - 1));
 58}
 59
 60/**
 61 * sel_ib_pkey_find - Search for a pkey record
 62 * @subnet_prefix: subnet_prefix
 63 * @pkey_num: pkey_num
 64 *
 65 * Description:
 66 * Search the pkey table and return the matching record.  If an entry
 67 * can not be found in the table return NULL.
 68 *
 69 */
 70static struct sel_ib_pkey *sel_ib_pkey_find(u64 subnet_prefix, u16 pkey_num)
 71{
 72	unsigned int idx;
 73	struct sel_ib_pkey *pkey;
 74
 75	idx = sel_ib_pkey_hashfn(pkey_num);
 76	list_for_each_entry_rcu(pkey, &sel_ib_pkey_hash[idx].list, list) {
 77		if (pkey->psec.pkey == pkey_num &&
 78		    pkey->psec.subnet_prefix == subnet_prefix)
 79			return pkey;
 80	}
 81
 82	return NULL;
 83}
 84
 85/**
 86 * sel_ib_pkey_insert - Insert a new pkey into the table
 87 * @pkey: the new pkey record
 88 *
 89 * Description:
 90 * Add a new pkey record to the hash table.
 91 *
 92 */
 93static void sel_ib_pkey_insert(struct sel_ib_pkey *pkey)
 94{
 95	unsigned int idx;
 96
 97	/* we need to impose a limit on the growth of the hash table so check
 98	 * this bucket to make sure it is within the specified bounds
 99	 */
100	idx = sel_ib_pkey_hashfn(pkey->psec.pkey);
101	list_add_rcu(&pkey->list, &sel_ib_pkey_hash[idx].list);
102	if (sel_ib_pkey_hash[idx].size == SEL_PKEY_HASH_BKT_LIMIT) {
103		struct sel_ib_pkey *tail;
104
105		tail = list_entry(
106			rcu_dereference_protected(
107				list_tail_rcu(&sel_ib_pkey_hash[idx].list),
108				lockdep_is_held(&sel_ib_pkey_lock)),
109			struct sel_ib_pkey, list);
110		list_del_rcu(&tail->list);
111		kfree_rcu(tail, rcu);
112	} else {
113		sel_ib_pkey_hash[idx].size++;
114	}
115}
116
117/**
118 * sel_ib_pkey_sid_slow - Lookup the SID of a pkey using the policy
119 * @subnet_prefix: subnet prefix
120 * @pkey_num: pkey number
121 * @sid: pkey SID
122 *
123 * Description:
124 * This function determines the SID of a pkey by querying the security
125 * policy.  The result is added to the pkey table to speedup future
126 * queries.  Returns zero on success, negative values on failure.
127 *
128 */
129static int sel_ib_pkey_sid_slow(u64 subnet_prefix, u16 pkey_num, u32 *sid)
130{
131	int ret;
132	struct sel_ib_pkey *pkey;
133	struct sel_ib_pkey *new = NULL;
134	unsigned long flags;
135
136	spin_lock_irqsave(&sel_ib_pkey_lock, flags);
137	pkey = sel_ib_pkey_find(subnet_prefix, pkey_num);
138	if (pkey) {
139		*sid = pkey->psec.sid;
140		spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
141		return 0;
142	}
143
144	ret = security_ib_pkey_sid(subnet_prefix, pkey_num,
145				   sid);
146	if (ret)
147		goto out;
148
149	/* If this memory allocation fails still return 0. The SID
150	 * is valid, it just won't be added to the cache.
151	 */
152	new = kzalloc(sizeof(*new), GFP_ATOMIC);
153	if (!new) {
154		ret = -ENOMEM;
155		goto out;
156	}
157
158	new->psec.subnet_prefix = subnet_prefix;
159	new->psec.pkey = pkey_num;
160	new->psec.sid = *sid;
161	sel_ib_pkey_insert(new);
162
163out:
164	spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
165	return ret;
166}
167
168/**
169 * sel_ib_pkey_sid - Lookup the SID of a PKEY
170 * @subnet_prefix: subnet_prefix
171 * @pkey_num: pkey number
172 * @sid: pkey SID
173 *
174 * Description:
175 * This function determines the SID of a PKEY using the fastest method
176 * possible.  First the pkey table is queried, but if an entry can't be found
177 * then the policy is queried and the result is added to the table to speedup
178 * future queries.  Returns zero on success, negative values on failure.
179 *
180 */
181int sel_ib_pkey_sid(u64 subnet_prefix, u16 pkey_num, u32 *sid)
182{
183	struct sel_ib_pkey *pkey;
184
185	rcu_read_lock();
186	pkey = sel_ib_pkey_find(subnet_prefix, pkey_num);
187	if (pkey) {
188		*sid = pkey->psec.sid;
189		rcu_read_unlock();
190		return 0;
191	}
192	rcu_read_unlock();
193
194	return sel_ib_pkey_sid_slow(subnet_prefix, pkey_num, sid);
195}
196
197/**
198 * sel_ib_pkey_flush - Flush the entire pkey table
199 *
200 * Description:
201 * Remove all entries from the pkey table
202 *
203 */
204void sel_ib_pkey_flush(void)
205{
206	unsigned int idx;
207	struct sel_ib_pkey *pkey, *pkey_tmp;
208	unsigned long flags;
209
210	spin_lock_irqsave(&sel_ib_pkey_lock, flags);
211	for (idx = 0; idx < SEL_PKEY_HASH_SIZE; idx++) {
212		list_for_each_entry_safe(pkey, pkey_tmp,
213					 &sel_ib_pkey_hash[idx].list, list) {
214			list_del_rcu(&pkey->list);
215			kfree_rcu(pkey, rcu);
216		}
217		sel_ib_pkey_hash[idx].size = 0;
218	}
219	spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
220}
221
222static __init int sel_ib_pkey_init(void)
223{
224	int iter;
225
226	if (!selinux_enabled_boot)
227		return 0;
228
229	for (iter = 0; iter < SEL_PKEY_HASH_SIZE; iter++) {
230		INIT_LIST_HEAD(&sel_ib_pkey_hash[iter].list);
231		sel_ib_pkey_hash[iter].size = 0;
232	}
233
234	return 0;
235}
236
237subsys_initcall(sel_ib_pkey_init);