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 .channel_lock = __SPIN_LOCK_UNLOCKED(&rxrpc_service_dummy_bundle.channel_lock), 15}; 16 17/* 18 * Find a service connection under RCU conditions. 19 * 20 * We could use a hash table, but that is subject to bucket stuffing by an 21 * attacker as the client gets to pick the epoch and cid values and would know 22 * the hash function. So, instead, we use a hash table for the peer and from 23 * that an rbtree to find the service connection. Under ordinary circumstances 24 * it might be slower than a large hash table, but it is at least limited in 25 * depth. 26 */ 27struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer, 28 struct sk_buff *skb) 29{ 30 struct rxrpc_connection *conn = NULL; 31 struct rxrpc_conn_proto k; 32 struct rxrpc_skb_priv *sp = rxrpc_skb(skb); 33 struct rb_node *p; 34 unsigned int seq = 1; 35 36 k.epoch = sp->hdr.epoch; 37 k.cid = sp->hdr.cid & RXRPC_CIDMASK; 38 39 do { 40 /* Unfortunately, rbtree walking doesn't give reliable results 41 * under just the RCU read lock, so we have to check for 42 * changes. 43 */ 44 seq++; /* 2 on the 1st/lockless path, otherwise odd */ 45 read_seqbegin_or_lock(&peer->service_conn_lock, &seq); 46 47 p = rcu_dereference_raw(peer->service_conns.rb_node); 48 while (p) { 49 conn = rb_entry(p, struct rxrpc_connection, service_node); 50 51 if (conn->proto.index_key < k.index_key) 52 p = rcu_dereference_raw(p->rb_left); 53 else if (conn->proto.index_key > k.index_key) 54 p = rcu_dereference_raw(p->rb_right); 55 else 56 break; 57 conn = NULL; 58 } 59 } while (need_seqretry(&peer->service_conn_lock, seq)); 60 61 done_seqretry(&peer->service_conn_lock, seq); 62 _leave(" = %d", conn ? conn->debug_id : -1); 63 return conn; 64} 65 66/* 67 * Insert a service connection into a peer's tree, thereby making it a target 68 * for incoming packets. 69 */ 70static void rxrpc_publish_service_conn(struct rxrpc_peer *peer, 71 struct rxrpc_connection *conn) 72{ 73 struct rxrpc_connection *cursor = NULL; 74 struct rxrpc_conn_proto k = conn->proto; 75 struct rb_node **pp, *parent; 76 77 write_seqlock_bh(&peer->service_conn_lock); 78 79 pp = &peer->service_conns.rb_node; 80 parent = NULL; 81 while (*pp) { 82 parent = *pp; 83 cursor = rb_entry(parent, 84 struct rxrpc_connection, service_node); 85 86 if (cursor->proto.index_key < k.index_key) 87 pp = &(*pp)->rb_left; 88 else if (cursor->proto.index_key > k.index_key) 89 pp = &(*pp)->rb_right; 90 else 91 goto found_extant_conn; 92 } 93 94 rb_link_node_rcu(&conn->service_node, parent, pp); 95 rb_insert_color(&conn->service_node, &peer->service_conns); 96conn_published: 97 set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags); 98 write_sequnlock_bh(&peer->service_conn_lock); 99 _leave(" = %d [new]", conn->debug_id); 100 return; 101 102found_extant_conn: 103 if (refcount_read(&cursor->ref) == 0) 104 goto replace_old_connection; 105 write_sequnlock_bh(&peer->service_conn_lock); 106 /* We should not be able to get here. rxrpc_incoming_connection() is 107 * called in a non-reentrant context, so there can't be a race to 108 * insert a new connection. 109 */ 110 BUG(); 111 112replace_old_connection: 113 /* The old connection is from an outdated epoch. */ 114 _debug("replace conn"); 115 rb_replace_node_rcu(&cursor->service_node, 116 &conn->service_node, 117 &peer->service_conns); 118 clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags); 119 goto conn_published; 120} 121 122/* 123 * Preallocate a service connection. The connection is placed on the proc and 124 * reap lists so that we don't have to get the lock from BH context. 125 */ 126struct rxrpc_connection *rxrpc_prealloc_service_connection(struct rxrpc_net *rxnet, 127 gfp_t gfp) 128{ 129 struct rxrpc_connection *conn = rxrpc_alloc_connection(gfp); 130 131 if (conn) { 132 /* We maintain an extra ref on the connection whilst it is on 133 * the rxrpc_connections list. 134 */ 135 conn->state = RXRPC_CONN_SERVICE_PREALLOC; 136 refcount_set(&conn->ref, 2); 137 conn->bundle = rxrpc_get_bundle(&rxrpc_service_dummy_bundle); 138 139 atomic_inc(&rxnet->nr_conns); 140 write_lock(&rxnet->conn_lock); 141 list_add_tail(&conn->link, &rxnet->service_conns); 142 list_add_tail(&conn->proc_link, &rxnet->conn_proc_list); 143 write_unlock(&rxnet->conn_lock); 144 145 trace_rxrpc_conn(conn->debug_id, rxrpc_conn_new_service, 146 refcount_read(&conn->ref), 147 __builtin_return_address(0)); 148 } 149 150 return conn; 151} 152 153/* 154 * Set up an incoming connection. This is called in BH context with the RCU 155 * read lock held. 156 */ 157void rxrpc_new_incoming_connection(struct rxrpc_sock *rx, 158 struct rxrpc_connection *conn, 159 const struct rxrpc_security *sec, 160 struct key *key, 161 struct sk_buff *skb) 162{ 163 struct rxrpc_skb_priv *sp = rxrpc_skb(skb); 164 165 _enter(""); 166 167 conn->proto.epoch = sp->hdr.epoch; 168 conn->proto.cid = sp->hdr.cid & RXRPC_CIDMASK; 169 conn->params.service_id = sp->hdr.serviceId; 170 conn->service_id = sp->hdr.serviceId; 171 conn->security_ix = sp->hdr.securityIndex; 172 conn->out_clientflag = 0; 173 conn->security = sec; 174 conn->server_key = key_get(key); 175 if (conn->security_ix) 176 conn->state = RXRPC_CONN_SERVICE_UNSECURED; 177 else 178 conn->state = RXRPC_CONN_SERVICE; 179 180 /* See if we should upgrade the service. This can only happen on the 181 * first packet on a new connection. Once done, it applies to all 182 * subsequent calls on that connection. 183 */ 184 if (sp->hdr.userStatus == RXRPC_USERSTATUS_SERVICE_UPGRADE && 185 conn->service_id == rx->service_upgrade.from) 186 conn->service_id = rx->service_upgrade.to; 187 188 /* Make the connection a target for incoming packets. */ 189 rxrpc_publish_service_conn(conn->params.peer, conn); 190 191 _net("CONNECTION new %d {%x}", conn->debug_id, conn->proto.cid); 192} 193 194/* 195 * Remove the service connection from the peer's tree, thereby removing it as a 196 * target for incoming packets. 197 */ 198void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn) 199{ 200 struct rxrpc_peer *peer = conn->params.peer; 201 202 write_seqlock_bh(&peer->service_conn_lock); 203 if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags)) 204 rb_erase(&conn->service_node, &peer->service_conns); 205 write_sequnlock_bh(&peer->service_conn_lock); 206} 207