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 static 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 */ 26 struct 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 */ 68 static 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); 94 conn_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; 99 100 found_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(); 109 110 replace_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 */ 124 struct 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 */ 154 void 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 */ 193 void 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 } 202