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 = 0;
  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                 read_seqbegin_or_lock(&peer->service_conn_lock, &seq);
  45
  46                 p = rcu_dereference_raw(peer->service_conns.rb_node);
  47                 while (p) {
  48                         conn = rb_entry(p, struct rxrpc_connection, service_node);
  49
  50                         if (conn->proto.index_key < k.index_key)
  51                                 p = rcu_dereference_raw(p->rb_left);
  52                         else if (conn->proto.index_key > k.index_key)
  53                                 p = rcu_dereference_raw(p->rb_right);
  54                         else
  55                                 break;
  56                         conn = NULL;
  57                 }
  58         } while (need_seqretry(&peer->service_conn_lock, seq));
  59
  60         done_seqretry(&peer->service_conn_lock, seq);
  61         _leave(" = %d", conn ? conn->debug_id : -1);
  62         return conn;
  63 }
  64
  65 /*
  66  * Insert a service connection into a peer's tree, thereby making it a target
  67  * for incoming packets.
  68  */
  69 static void rxrpc_publish_service_conn(struct rxrpc_peer *peer,
  70                                        struct rxrpc_connection *conn)
  71 {
  72         struct rxrpc_connection *cursor = NULL;
  73         struct rxrpc_conn_proto k = conn->proto;
  74         struct rb_node **pp, *parent;
  75
  76         write_seqlock_bh(&peer->service_conn_lock);
  77
  78         pp = &peer->service_conns.rb_node;
  79         parent = NULL;
  80         while (*pp) {
  81                 parent = *pp;
  82                 cursor = rb_entry(parent,
  83                                   struct rxrpc_connection, service_node);
  84
  85                 if (cursor->proto.index_key < k.index_key)
  86                         pp = &(*pp)->rb_left;
  87                 else if (cursor->proto.index_key > k.index_key)
  88                         pp = &(*pp)->rb_right;
  89                 else
  90                         goto found_extant_conn;
  91         }
  92
  93         rb_link_node_rcu(&conn->service_node, parent, pp);
  94         rb_insert_color(&conn->service_node, &peer->service_conns);
  95 conn_published:
  96         set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags);
  97         write_sequnlock_bh(&peer->service_conn_lock);
  98         _leave(" = %d [new]", conn->debug_id);
  99         return;
 100
 101 found_extant_conn:
 102         if (refcount_read(&cursor->ref) == 0)
 103                 goto replace_old_connection;
 104         write_sequnlock_bh(&peer->service_conn_lock);
 105         /* We should not be able to get here.  rxrpc_incoming_connection() is
 106          * called in a non-reentrant context, so there can't be a race to
 107          * insert a new connection.
 108          */
 109         BUG();
 110
 111 replace_old_connection:
 112         /* The old connection is from an outdated epoch. */
 113         _debug("replace conn");
 114         rb_replace_node_rcu(&cursor->service_node,
 115                             &conn->service_node,
 116                             &peer->service_conns);
 117         clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags);
 118         goto conn_published;
 119 }
 120
 121 /*
 122  * Preallocate a service connection.  The connection is placed on the proc and
 123  * reap lists so that we don't have to get the lock from BH context.
 124  */
 125 struct rxrpc_connection *rxrpc_prealloc_service_connection(struct rxrpc_net *rxnet,
 126                                                            gfp_t gfp)
 127 {
 128         struct rxrpc_connection *conn = rxrpc_alloc_connection(gfp);
 129
 130         if (conn) {
 131                 /* We maintain an extra ref on the connection whilst it is on
 132                  * the rxrpc_connections list.
 133                  */
 134                 conn->state = RXRPC_CONN_SERVICE_PREALLOC;
 135                 refcount_set(&conn->ref, 2);
 136                 conn->bundle = rxrpc_get_bundle(&rxrpc_service_dummy_bundle);
 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                 trace_rxrpc_conn(conn->debug_id, rxrpc_conn_new_service,
 145                                  refcount_read(&conn->ref),
 146                                  __builtin_return_address(0));
 147         }
 148
 149         return conn;
 150 }
 151
 152 /*
 153  * Set up an incoming connection.  This is called in BH context with the RCU
 154  * read lock held.
 155  */
 156 void rxrpc_new_incoming_connection(struct rxrpc_sock *rx,
 157                                    struct rxrpc_connection *conn,
 158                                    const struct rxrpc_security *sec,
 159                                    struct sk_buff *skb)
 160 {
 161         struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 162
 163         _enter("");
 164
 165         conn->proto.epoch       = sp->hdr.epoch;
 166         conn->proto.cid         = sp->hdr.cid & RXRPC_CIDMASK;
 167         conn->params.service_id = sp->hdr.serviceId;
 168         conn->service_id        = sp->hdr.serviceId;
 169         conn->security_ix       = sp->hdr.securityIndex;
 170         conn->out_clientflag    = 0;
 171         conn->security          = sec;
 172         if (conn->security_ix)
 173                 conn->state     = RXRPC_CONN_SERVICE_UNSECURED;
 174         else
 175                 conn->state     = RXRPC_CONN_SERVICE;
 176
 177         /* See if we should upgrade the service.  This can only happen on the
 178          * first packet on a new connection.  Once done, it applies to all
 179          * subsequent calls on that connection.
 180          */
 181         if (sp->hdr.userStatus == RXRPC_USERSTATUS_SERVICE_UPGRADE &&
 182             conn->service_id == rx->service_upgrade.from)
 183                 conn->service_id = rx->service_upgrade.to;
 184
 185         /* Make the connection a target for incoming packets. */
 186         rxrpc_publish_service_conn(conn->params.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->params.peer;
 196
 197         write_seqlock_bh(&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_bh(&peer->service_conn_lock);
 201 }