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 };
  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 }