1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Service connection management
3 *
4 * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/slab.h>
9 #include "ar-internal.h"
10
11 static struct rxrpc_bundle rxrpc_service_dummy_bundle = {
12 .ref = REFCOUNT_INIT(1),
13 .debug_id = UINT_MAX,
14 .channel_lock = __SPIN_LOCK_UNLOCKED(&rxrpc_service_dummy_bundle.channel_lock),
15 };
16
17 /*
18 * Find a service connection under RCU conditions.
19 *
20 * We could use a hash table, but that is subject to bucket stuffing by an
21 * attacker as the client gets to pick the epoch and cid values and would know
22 * the hash function. So, instead, we use a hash table for the peer and from
23 * that an rbtree to find the service connection. Under ordinary circumstances
24 * it might be slower than a large hash table, but it is at least limited in
25 * depth.
26 */
rxrpc_find_service_conn_rcu(struct rxrpc_peer * peer,struct sk_buff * skb)27 struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
28 struct sk_buff *skb)
29 {
30 struct rxrpc_connection *conn = NULL;
31 struct rxrpc_conn_proto k;
32 struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
33 struct rb_node *p;
34 unsigned int seq = 1;
35
36 k.epoch = sp->hdr.epoch;
37 k.cid = sp->hdr.cid & RXRPC_CIDMASK;
38
39 do {
40 /* Unfortunately, rbtree walking doesn't give reliable results
41 * under just the RCU read lock, so we have to check for
42 * changes.
43 */
44 seq++; /* 2 on the 1st/lockless path, otherwise odd */
45 read_seqbegin_or_lock(&peer->service_conn_lock, &seq);
46
47 p = rcu_dereference_raw(peer->service_conns.rb_node);
48 while (p) {
49 conn = rb_entry(p, struct rxrpc_connection, service_node);
50
51 if (conn->proto.index_key < k.index_key)
52 p = rcu_dereference_raw(p->rb_left);
53 else if (conn->proto.index_key > k.index_key)
54 p = rcu_dereference_raw(p->rb_right);
55 else
56 break;
57 conn = NULL;
58 }
59 } while (need_seqretry(&peer->service_conn_lock, seq));
60
61 done_seqretry(&peer->service_conn_lock, seq);
62 _leave(" = %d", conn ? conn->debug_id : -1);
63 return conn;
64 }
65
66 /*
67 * Insert a service connection into a peer's tree, thereby making it a target
68 * for incoming packets.
69 */
rxrpc_publish_service_conn(struct rxrpc_peer * peer,struct rxrpc_connection * conn)70 static void rxrpc_publish_service_conn(struct rxrpc_peer *peer,
71 struct rxrpc_connection *conn)
72 {
73 struct rxrpc_connection *cursor = NULL;
74 struct rxrpc_conn_proto k = conn->proto;
75 struct rb_node **pp, *parent;
76
77 write_seqlock_bh(&peer->service_conn_lock);
78
79 pp = &peer->service_conns.rb_node;
80 parent = NULL;
81 while (*pp) {
82 parent = *pp;
83 cursor = rb_entry(parent,
84 struct rxrpc_connection, service_node);
85
86 if (cursor->proto.index_key < k.index_key)
87 pp = &(*pp)->rb_left;
88 else if (cursor->proto.index_key > k.index_key)
89 pp = &(*pp)->rb_right;
90 else
91 goto found_extant_conn;
92 }
93
94 rb_link_node_rcu(&conn->service_node, parent, pp);
95 rb_insert_color(&conn->service_node, &peer->service_conns);
96 conn_published:
97 set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags);
98 write_sequnlock_bh(&peer->service_conn_lock);
99 _leave(" = %d [new]", conn->debug_id);
100 return;
101
102 found_extant_conn:
103 if (refcount_read(&cursor->ref) == 0)
104 goto replace_old_connection;
105 write_sequnlock_bh(&peer->service_conn_lock);
106 /* We should not be able to get here. rxrpc_incoming_connection() is
107 * called in a non-reentrant context, so there can't be a race to
108 * insert a new connection.
109 */
110 BUG();
111
112 replace_old_connection:
113 /* The old connection is from an outdated epoch. */
114 _debug("replace conn");
115 rb_replace_node_rcu(&cursor->service_node,
116 &conn->service_node,
117 &peer->service_conns);
118 clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags);
119 goto conn_published;
120 }
121
122 /*
123 * Preallocate a service connection. The connection is placed on the proc and
124 * reap lists so that we don't have to get the lock from BH context.
125 */
rxrpc_prealloc_service_connection(struct rxrpc_net * rxnet,gfp_t gfp)126 struct rxrpc_connection *rxrpc_prealloc_service_connection(struct rxrpc_net *rxnet,
127 gfp_t gfp)
128 {
129 struct rxrpc_connection *conn = rxrpc_alloc_connection(gfp);
130
131 if (conn) {
132 /* We maintain an extra ref on the connection whilst it is on
133 * the rxrpc_connections list.
134 */
135 conn->state = RXRPC_CONN_SERVICE_PREALLOC;
136 refcount_set(&conn->ref, 2);
137 conn->bundle = rxrpc_get_bundle(&rxrpc_service_dummy_bundle);
138
139 atomic_inc(&rxnet->nr_conns);
140 write_lock(&rxnet->conn_lock);
141 list_add_tail(&conn->link, &rxnet->service_conns);
142 list_add_tail(&conn->proc_link, &rxnet->conn_proc_list);
143 write_unlock(&rxnet->conn_lock);
144
145 trace_rxrpc_conn(conn->debug_id, rxrpc_conn_new_service,
146 refcount_read(&conn->ref),
147 __builtin_return_address(0));
148 }
149
150 return conn;
151 }
152
153 /*
154 * Set up an incoming connection. This is called in BH context with the RCU
155 * read lock held.
156 */
rxrpc_new_incoming_connection(struct rxrpc_sock * rx,struct rxrpc_connection * conn,const struct rxrpc_security * sec,struct key * key,struct sk_buff * skb)157 void rxrpc_new_incoming_connection(struct rxrpc_sock *rx,
158 struct rxrpc_connection *conn,
159 const struct rxrpc_security *sec,
160 struct key *key,
161 struct sk_buff *skb)
162 {
163 struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
164
165 _enter("");
166
167 conn->proto.epoch = sp->hdr.epoch;
168 conn->proto.cid = sp->hdr.cid & RXRPC_CIDMASK;
169 conn->params.service_id = sp->hdr.serviceId;
170 conn->service_id = sp->hdr.serviceId;
171 conn->security_ix = sp->hdr.securityIndex;
172 conn->out_clientflag = 0;
173 conn->security = sec;
174 conn->server_key = key_get(key);
175 if (conn->security_ix)
176 conn->state = RXRPC_CONN_SERVICE_UNSECURED;
177 else
178 conn->state = RXRPC_CONN_SERVICE;
179
180 /* See if we should upgrade the service. This can only happen on the
181 * first packet on a new connection. Once done, it applies to all
182 * subsequent calls on that connection.
183 */
184 if (sp->hdr.userStatus == RXRPC_USERSTATUS_SERVICE_UPGRADE &&
185 conn->service_id == rx->service_upgrade.from)
186 conn->service_id = rx->service_upgrade.to;
187
188 /* Make the connection a target for incoming packets. */
189 rxrpc_publish_service_conn(conn->params.peer, conn);
190
191 _net("CONNECTION new %d {%x}", conn->debug_id, conn->proto.cid);
192 }
193
194 /*
195 * Remove the service connection from the peer's tree, thereby removing it as a
196 * target for incoming packets.
197 */
rxrpc_unpublish_service_conn(struct rxrpc_connection * conn)198 void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn)
199 {
200 struct rxrpc_peer *peer = conn->params.peer;
201
202 write_seqlock_bh(&peer->service_conn_lock);
203 if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags))
204 rb_erase(&conn->service_node, &peer->service_conns);
205 write_sequnlock_bh(&peer->service_conn_lock);
206 }
207