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