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101 * insert a new connection. 102 */ 103 BUG(); 104 105 replace_old_connection: 106 /* The old connection is from an outdated epoch.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