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 .usage = ATOMIC_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 = 0;
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 read_seqbegin_or_lock(&peer->service_conn_lock, &seq);
45
46 p = rcu_dereference_raw(peer->service_conns.rb_node);
47 while (p) {
48 conn = rb_entry(p, struct rxrpc_connection, service_node);
49
50 if (conn->proto.index_key < k.index_key)
51 p = rcu_dereference_raw(p->rb_left);
52 else if (conn->proto.index_key > k.index_key)
53 p = rcu_dereference_raw(p->rb_right);
54 else
55 break;
56 conn = NULL;
57 }
58 } while (need_seqretry(&peer->service_conn_lock, seq));
59
60 done_seqretry(&peer->service_conn_lock, seq);
61 _leave(" = %d", conn ? conn->debug_id : -1);
62 return conn;
63 }
64
65 /*
66 * Insert a service connection into a peer's tree, thereby making it a target
67 * for incoming packets.
68 */
rxrpc_publish_service_conn(struct rxrpc_peer * peer,struct rxrpc_connection * conn)69 static void rxrpc_publish_service_conn(struct rxrpc_peer *peer,
70 struct rxrpc_connection *conn)
71 {
72 struct rxrpc_connection *cursor = NULL;
73 struct rxrpc_conn_proto k = conn->proto;
74 struct rb_node **pp, *parent;
75
76 write_seqlock_bh(&peer->service_conn_lock);
77
78 pp = &peer->service_conns.rb_node;
79 parent = NULL;
80 while (*pp) {
81 parent = *pp;
82 cursor = rb_entry(parent,
83 struct rxrpc_connection, service_node);
84
85 if (cursor->proto.index_key < k.index_key)
86 pp = &(*pp)->rb_left;
87 else if (cursor->proto.index_key > k.index_key)
88 pp = &(*pp)->rb_right;
89 else
90 goto found_extant_conn;
91 }
92
93 rb_link_node_rcu(&conn->service_node, parent, pp);
94 rb_insert_color(&conn->service_node, &peer->service_conns);
95 conn_published:
96 set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags);
97 write_sequnlock_bh(&peer->service_conn_lock);
98 _leave(" = %d [new]", conn->debug_id);
99 return;
100
101 found_extant_conn:
102 if (atomic_read(&cursor->usage) == 0)
103 goto replace_old_connection;
104 write_sequnlock_bh(&peer->service_conn_lock);
105 /* We should not be able to get here. rxrpc_incoming_connection() is
106 * called in a non-reentrant context, so there can't be a race to
107 * insert a new connection.
108 */
109 BUG();
110
111 replace_old_connection:
112 /* The old connection is from an outdated epoch. */
113 _debug("replace conn");
114 rb_replace_node_rcu(&cursor->service_node,
115 &conn->service_node,
116 &peer->service_conns);
117 clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags);
118 goto conn_published;
119 }
120
121 /*
122 * Preallocate a service connection. The connection is placed on the proc and
123 * reap lists so that we don't have to get the lock from BH context.
124 */
rxrpc_prealloc_service_connection(struct rxrpc_net * rxnet,gfp_t gfp)125 struct rxrpc_connection *rxrpc_prealloc_service_connection(struct rxrpc_net *rxnet,
126 gfp_t gfp)
127 {
128 struct rxrpc_connection *conn = rxrpc_alloc_connection(gfp);
129
130 if (conn) {
131 /* We maintain an extra ref on the connection whilst it is on
132 * the rxrpc_connections list.
133 */
134 conn->state = RXRPC_CONN_SERVICE_PREALLOC;
135 atomic_set(&conn->usage, 2);
136 conn->bundle = rxrpc_get_bundle(&rxrpc_service_dummy_bundle);
137
138 atomic_inc(&rxnet->nr_conns);
139 write_lock(&rxnet->conn_lock);
140 list_add_tail(&conn->link, &rxnet->service_conns);
141 list_add_tail(&conn->proc_link, &rxnet->conn_proc_list);
142 write_unlock(&rxnet->conn_lock);
143
144 trace_rxrpc_conn(conn->debug_id, rxrpc_conn_new_service,
145 atomic_read(&conn->usage),
146 __builtin_return_address(0));
147 }
148
149 return conn;
150 }
151
152 /*
153 * Set up an incoming connection. This is called in BH context with the RCU
154 * read lock held.
155 */
rxrpc_new_incoming_connection(struct rxrpc_sock * rx,struct rxrpc_connection * conn,const struct rxrpc_security * sec,struct sk_buff * skb)156 void rxrpc_new_incoming_connection(struct rxrpc_sock *rx,
157 struct rxrpc_connection *conn,
158 const struct rxrpc_security *sec,
159 struct sk_buff *skb)
160 {
161 struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
162
163 _enter("");
164
165 conn->proto.epoch = sp->hdr.epoch;
166 conn->proto.cid = sp->hdr.cid & RXRPC_CIDMASK;
167 conn->params.service_id = sp->hdr.serviceId;
168 conn->service_id = sp->hdr.serviceId;
169 conn->security_ix = sp->hdr.securityIndex;
170 conn->out_clientflag = 0;
171 conn->security = sec;
172 if (conn->security_ix)
173 conn->state = RXRPC_CONN_SERVICE_UNSECURED;
174 else
175 conn->state = RXRPC_CONN_SERVICE;
176
177 /* See if we should upgrade the service. This can only happen on the
178 * first packet on a new connection. Once done, it applies to all
179 * subsequent calls on that connection.
180 */
181 if (sp->hdr.userStatus == RXRPC_USERSTATUS_SERVICE_UPGRADE &&
182 conn->service_id == rx->service_upgrade.from)
183 conn->service_id = rx->service_upgrade.to;
184
185 /* Make the connection a target for incoming packets. */
186 rxrpc_publish_service_conn(conn->params.peer, conn);
187
188 _net("CONNECTION new %d {%x}", conn->debug_id, conn->proto.cid);
189 }
190
191 /*
192 * Remove the service connection from the peer's tree, thereby removing it as a
193 * target for incoming packets.
194 */
rxrpc_unpublish_service_conn(struct rxrpc_connection * conn)195 void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn)
196 {
197 struct rxrpc_peer *peer = conn->params.peer;
198
199 write_seqlock_bh(&peer->service_conn_lock);
200 if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags))
201 rb_erase(&conn->service_node, &peer->service_conns);
202 write_sequnlock_bh(&peer->service_conn_lock);
203 }
204
