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