net/rxrpc/conn_service.c

   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         .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  */
  27 struct 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  */
  70 static 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);
  96 conn_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
 102 found_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
 112 replace_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  */
 126 struct 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  */
 157 void 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  */
 198 void 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 }