1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
|
/* Service connection management
*
* Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/slab.h>
#include "ar-internal.h"
/*
* Find a service connection under RCU conditions.
*
* We could use a hash table, but that is subject to bucket stuffing by an
* attacker as the client gets to pick the epoch and cid values and would know
* the hash function. So, instead, we use a hash table for the peer and from
* that an rbtree to find the service connection. Under ordinary circumstances
* it might be slower than a large hash table, but it is at least limited in
* depth.
*/
struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
struct sk_buff *skb)
{
struct rxrpc_connection *conn = NULL;
struct rxrpc_conn_proto k;
struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
struct rb_node *p;
unsigned int seq = 0;
k.epoch = sp->hdr.epoch;
k.cid = sp->hdr.cid & RXRPC_CIDMASK;
do {
/* Unfortunately, rbtree walking doesn't give reliable results
* under just the RCU read lock, so we have to check for
* changes.
*/
read_seqbegin_or_lock(&peer->service_conn_lock, &seq);
p = rcu_dereference_raw(peer->service_conns.rb_node);
while (p) {
conn = rb_entry(p, struct rxrpc_connection, service_node);
if (conn->proto.index_key < k.index_key)
p = rcu_dereference_raw(p->rb_left);
else if (conn->proto.index_key > k.index_key)
p = rcu_dereference_raw(p->rb_right);
else
goto done;
conn = NULL;
}
} while (need_seqretry(&peer->service_conn_lock, seq));
done:
done_seqretry(&peer->service_conn_lock, seq);
_leave(" = %d", conn ? conn->debug_id : -1);
return conn;
}
/*
* Insert a service connection into a peer's tree, thereby making it a target
* for incoming packets.
*/
static struct rxrpc_connection *
rxrpc_publish_service_conn(struct rxrpc_peer *peer,
struct rxrpc_connection *conn)
{
struct rxrpc_connection *cursor = NULL;
struct rxrpc_conn_proto k = conn->proto;
struct rb_node **pp, *parent;
write_seqlock_bh(&peer->service_conn_lock);
pp = &peer->service_conns.rb_node;
parent = NULL;
while (*pp) {
parent = *pp;
cursor = rb_entry(parent,
struct rxrpc_connection, service_node);
if (cursor->proto.index_key < k.index_key)
pp = &(*pp)->rb_left;
else if (cursor->proto.index_key > k.index_key)
pp = &(*pp)->rb_right;
else
goto found_extant_conn;
}
rb_link_node_rcu(&conn->service_node, parent, pp);
rb_insert_color(&conn->service_node, &peer->service_conns);
conn_published:
set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags);
write_sequnlock_bh(&peer->service_conn_lock);
_leave(" = %d [new]", conn->debug_id);
return conn;
found_extant_conn:
if (atomic_read(&cursor->usage) == 0)
goto replace_old_connection;
write_sequnlock_bh(&peer->service_conn_lock);
/* We should not be able to get here. rxrpc_incoming_connection() is
* called in a non-reentrant context, so there can't be a race to
* insert a new connection.
*/
BUG();
replace_old_connection:
/* The old connection is from an outdated epoch. */
_debug("replace conn");
rb_replace_node_rcu(&cursor->service_node,
&conn->service_node,
&peer->service_conns);
clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags);
goto conn_published;
}
/*
* get a record of an incoming connection
*/
struct rxrpc_connection *rxrpc_incoming_connection(struct rxrpc_local *local,
struct sockaddr_rxrpc *srx,
struct sk_buff *skb)
{
struct rxrpc_connection *conn;
struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
struct rxrpc_peer *peer;
const char *new = "old";
_enter("");
peer = rxrpc_lookup_peer(local, srx, GFP_NOIO);
if (!peer) {
_debug("no peer");
return ERR_PTR(-EBUSY);
}
ASSERT(sp->hdr.flags & RXRPC_CLIENT_INITIATED);
rcu_read_lock();
peer = rxrpc_lookup_peer_rcu(local, srx);
if (peer) {
conn = rxrpc_find_service_conn_rcu(peer, skb);
if (conn) {
if (sp->hdr.securityIndex != conn->security_ix)
goto security_mismatch_rcu;
if (rxrpc_get_connection_maybe(conn))
goto found_extant_connection_rcu;
/* The conn has expired but we can't remove it without
* the appropriate lock, so we attempt to replace it
* when we have a new candidate.
*/
}
if (!rxrpc_get_peer_maybe(peer))
peer = NULL;
}
rcu_read_unlock();
if (!peer) {
peer = rxrpc_lookup_peer(local, srx, GFP_NOIO);
if (!peer)
goto enomem;
}
/* We don't have a matching record yet. */
conn = rxrpc_alloc_connection(GFP_NOIO);
if (!conn)
goto enomem_peer;
conn->proto.epoch = sp->hdr.epoch;
conn->proto.cid = sp->hdr.cid & RXRPC_CIDMASK;
conn->params.local = local;
conn->params.peer = peer;
conn->params.service_id = sp->hdr.serviceId;
conn->security_ix = sp->hdr.securityIndex;
conn->out_clientflag = 0;
conn->state = RXRPC_CONN_SERVICE;
if (conn->params.service_id)
conn->state = RXRPC_CONN_SERVICE_UNSECURED;
rxrpc_get_local(local);
write_lock(&rxrpc_connection_lock);
list_add_tail(&conn->link, &rxrpc_connections);
write_unlock(&rxrpc_connection_lock);
/* Make the connection a target for incoming packets. */
rxrpc_publish_service_conn(peer, conn);
new = "new";
success:
_net("CONNECTION %s %d {%x}", new, conn->debug_id, conn->proto.cid);
_leave(" = %p {u=%d}", conn, atomic_read(&conn->usage));
return conn;
found_extant_connection_rcu:
rcu_read_unlock();
goto success;
security_mismatch_rcu:
rcu_read_unlock();
_leave(" = -EKEYREJECTED");
return ERR_PTR(-EKEYREJECTED);
enomem_peer:
rxrpc_put_peer(peer);
enomem:
_leave(" = -ENOMEM");
return ERR_PTR(-ENOMEM);
}
/*
* Remove the service connection from the peer's tree, thereby removing it as a
* target for incoming packets.
*/
void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn)
{
struct rxrpc_peer *peer = conn->params.peer;
write_seqlock_bh(&peer->service_conn_lock);
if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags))
rb_erase(&conn->service_node, &peer->service_conns);
write_sequnlock_bh(&peer->service_conn_lock);
}
|
