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);
238