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 */ 25 struct 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 goto done; 54 conn = NULL; 55 } 56 } while (need_seqretry(&peer->service_conn_lock, seq)); 57 58 done: 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 */ 68 static struct rxrpc_connection * 69 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 conn; 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 * get a record of an incoming connection 123 */ 124 struct rxrpc_connection *rxrpc_incoming_connection(struct rxrpc_local *local, 125 struct sockaddr_rxrpc *srx, 126 struct sk_buff *skb) 127 { 128 struct rxrpc_connection *conn; 129 struct rxrpc_skb_priv *sp = rxrpc_skb(skb); 130 struct rxrpc_peer *peer; 131 const char *new = "old"; 132 133 _enter(""); 134 135 peer = rxrpc_lookup_peer(local, srx, GFP_NOIO); 136 if (!peer) { 137 _debug("no peer"); 138 return ERR_PTR(-EBUSY); 139 } 140 141 ASSERT(sp->hdr.flags & RXRPC_CLIENT_INITIATED); 142 143 rcu_read_lock(); 144 peer = rxrpc_lookup_peer_rcu(local, srx); 145 if (peer) { 146 conn = rxrpc_find_service_conn_rcu(peer, skb); 147 if (conn) { 148 if (sp->hdr.securityIndex != conn->security_ix) 149 goto security_mismatch_rcu; 150 if (rxrpc_get_connection_maybe(conn)) 151 goto found_extant_connection_rcu; 152 153 /* The conn has expired but we can't remove it without 154 * the appropriate lock, so we attempt to replace it 155 * when we have a new candidate. 156 */ 157 } 158 159 if (!rxrpc_get_peer_maybe(peer)) 160 peer = NULL; 161 } 162 rcu_read_unlock(); 163 164 if (!peer) { 165 peer = rxrpc_lookup_peer(local, srx, GFP_NOIO); 166 if (!peer) 167 goto enomem; 168 } 169 170 /* We don't have a matching record yet. */ 171 conn = rxrpc_alloc_connection(GFP_NOIO); 172 if (!conn) 173 goto enomem_peer; 174 175 conn->proto.epoch = sp->hdr.epoch; 176 conn->proto.cid = sp->hdr.cid & RXRPC_CIDMASK; 177 conn->params.local = local; 178 conn->params.peer = peer; 179 conn->params.service_id = sp->hdr.serviceId; 180 conn->security_ix = sp->hdr.securityIndex; 181 conn->out_clientflag = 0; 182 conn->state = RXRPC_CONN_SERVICE; 183 if (conn->params.service_id) 184 conn->state = RXRPC_CONN_SERVICE_UNSECURED; 185 186 rxrpc_get_local(local); 187 188 write_lock(&rxrpc_connection_lock); 189 list_add_tail(&conn->link, &rxrpc_connections); 190 write_unlock(&rxrpc_connection_lock); 191 192 /* Make the connection a target for incoming packets. */ 193 rxrpc_publish_service_conn(peer, conn); 194 195 new = "new"; 196 197 success: 198 _net("CONNECTION %s %d {%x}", new, conn->debug_id, conn->proto.cid); 199 _leave(" = %p {u=%d}", conn, atomic_read(&conn->usage)); 200 return conn; 201 202 found_extant_connection_rcu: 203 rcu_read_unlock(); 204 goto success; 205 206 security_mismatch_rcu: 207 rcu_read_unlock(); 208 _leave(" = -EKEYREJECTED"); 209 return ERR_PTR(-EKEYREJECTED); 210 211 enomem_peer: 212 rxrpc_put_peer(peer); 213 enomem: 214 _leave(" = -ENOMEM"); 215 return ERR_PTR(-ENOMEM); 216 } 217 218 /* 219 * Remove the service connection from the peer's tree, thereby removing it as a 220 * target for incoming packets. 221 */ 222 void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn) 223 { 224 struct rxrpc_peer *peer = conn->params.peer; 225 226 write_seqlock_bh(&peer->service_conn_lock); 227 if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags)) 228 rb_erase(&conn->service_node, &peer->service_conns); 229 write_sequnlock_bh(&peer->service_conn_lock); 230 } 231