[mirror_ubuntu-focal-kernel.git] / net / rxrpc / conn_service.c

/* Service connection management
 *
 * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/slab.h>
#include "ar-internal.h"

/*
 * Find a service connection under RCU conditions.
 *
 * We could use a hash table, but that is subject to bucket stuffing by an
 * attacker as the client gets to pick the epoch and cid values and would know
 * the hash function.  So, instead, we use a hash table for the peer and from
 * that an rbtree to find the service connection.  Under ordinary circumstances
 * it might be slower than a large hash table, but it is at least limited in
 * depth.
 */
struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
						     struct sk_buff *skb)
{
	struct rxrpc_connection *conn = NULL;
	struct rxrpc_conn_proto k;
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	struct rb_node *p;
	unsigned int seq = 0;

	k.epoch	= sp->hdr.epoch;
	k.cid	= sp->hdr.cid & RXRPC_CIDMASK;

	do {
		/* Unfortunately, rbtree walking doesn't give reliable results
		 * under just the RCU read lock, so we have to check for
		 * changes.
		 */
		read_seqbegin_or_lock(&peer->service_conn_lock, &seq);

		p = rcu_dereference_raw(peer->service_conns.rb_node);
		while (p) {
			conn = rb_entry(p, struct rxrpc_connection, service_node);

			if (conn->proto.index_key < k.index_key)
				p = rcu_dereference_raw(p->rb_left);
			else if (conn->proto.index_key > k.index_key)
				p = rcu_dereference_raw(p->rb_right);
			else
				break;
			conn = NULL;
		}
	} while (need_seqretry(&peer->service_conn_lock, seq));

	done_seqretry(&peer->service_conn_lock, seq);
	_leave(" = %d", conn ? conn->debug_id : -1);
	return conn;
}

/*
 * Insert a service connection into a peer's tree, thereby making it a target
 * for incoming packets.
 */
static void rxrpc_publish_service_conn(struct rxrpc_peer *peer,
				       struct rxrpc_connection *conn)
{
	struct rxrpc_connection *cursor = NULL;
	struct rxrpc_conn_proto k = conn->proto;
	struct rb_node **pp, *parent;

	write_seqlock_bh(&peer->service_conn_lock);

	pp = &peer->service_conns.rb_node;
	parent = NULL;
	while (*pp) {
		parent = *pp;
		cursor = rb_entry(parent,
				  struct rxrpc_connection, service_node);

		if (cursor->proto.index_key < k.index_key)
			pp = &(*pp)->rb_left;
		else if (cursor->proto.index_key > k.index_key)
			pp = &(*pp)->rb_right;
		else
			goto found_extant_conn;
	}

	rb_link_node_rcu(&conn->service_node, parent, pp);
	rb_insert_color(&conn->service_node, &peer->service_conns);
conn_published:
	set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags);
	write_sequnlock_bh(&peer->service_conn_lock);
	_leave(" = %d [new]", conn->debug_id);
	return;

found_extant_conn:
	if (atomic_read(&cursor->usage) == 0)
		goto replace_old_connection;
	write_sequnlock_bh(&peer->service_conn_lock);
	/* We should not be able to get here.  rxrpc_incoming_connection() is
	 * called in a non-reentrant context, so there can't be a race to
	 * insert a new connection.
	 */
	BUG();

replace_old_connection:
	/* The old connection is from an outdated epoch. */
	_debug("replace conn");
	rb_replace_node_rcu(&cursor->service_node,
			    &conn->service_node,
			    &peer->service_conns);
	clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags);
	goto conn_published;
}

/*
 * Preallocate a service connection.  The connection is placed on the proc and
 * reap lists so that we don't have to get the lock from BH context.
 */
struct rxrpc_connection *rxrpc_prealloc_service_connection(struct rxrpc_net *rxnet,
							   gfp_t gfp)
{
	struct rxrpc_connection *conn = rxrpc_alloc_connection(gfp);

	if (conn) {
		/* We maintain an extra ref on the connection whilst it is on
		 * the rxrpc_connections list.
		 */
		conn->state = RXRPC_CONN_SERVICE_PREALLOC;
		atomic_set(&conn->usage, 2);

		atomic_inc(&rxnet->nr_conns);
		write_lock(&rxnet->conn_lock);
		list_add_tail(&conn->link, &rxnet->service_conns);
		list_add_tail(&conn->proc_link, &rxnet->conn_proc_list);
		write_unlock(&rxnet->conn_lock);

		trace_rxrpc_conn(conn, rxrpc_conn_new_service,
				 atomic_read(&conn->usage),
				 __builtin_return_address(0));
	}

	return conn;
}

/*
 * Set up an incoming connection.  This is called in BH context with the RCU
 * read lock held.
 */
void rxrpc_new_incoming_connection(struct rxrpc_sock *rx,
				   struct rxrpc_connection *conn,
				   struct sk_buff *skb)
{
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);

	_enter("");

	conn->proto.epoch	= sp->hdr.epoch;
	conn->proto.cid		= sp->hdr.cid & RXRPC_CIDMASK;
	conn->params.service_id	= sp->hdr.serviceId;
	conn->service_id	= sp->hdr.serviceId;
	conn->security_ix	= sp->hdr.securityIndex;
	conn->out_clientflag	= 0;
	if (conn->security_ix)
		conn->state	= RXRPC_CONN_SERVICE_UNSECURED;
	else
		conn->state	= RXRPC_CONN_SERVICE;

	/* See if we should upgrade the service.  This can only happen on the
	 * first packet on a new connection.  Once done, it applies to all
	 * subsequent calls on that connection.
	 */
	if (sp->hdr.userStatus == RXRPC_USERSTATUS_SERVICE_UPGRADE &&
	    conn->service_id == rx->service_upgrade.from)
		conn->service_id = rx->service_upgrade.to;

	/* Make the connection a target for incoming packets. */
	rxrpc_publish_service_conn(conn->params.peer, conn);

	_net("CONNECTION new %d {%x}", conn->debug_id, conn->proto.cid);
}

/*
 * Remove the service connection from the peer's tree, thereby removing it as a
 * target for incoming packets.
 */
void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn)
{
	struct rxrpc_peer *peer = conn->params.peer;

	write_seqlock_bh(&peer->service_conn_lock);
	if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags))
		rb_erase(&conn->service_node, &peer->service_conns);
	write_sequnlock_bh(&peer->service_conn_lock);
}
Commit	Line	Data
7877a4a4 DH	1	/* Service connection management
	2	*
	3	* Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public Licence
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the Licence, or (at your option) any later version.
	10	*/
	11
	12	#include <linux/slab.h>
	13	#include "ar-internal.h"
	14
8496af50 DH	15	/*
	16	* Find a service connection under RCU conditions.
	17	*
	18	* We could use a hash table, but that is subject to bucket stuffing by an
	19	* attacker as the client gets to pick the epoch and cid values and would know
	20	* the hash function. So, instead, we use a hash table for the peer and from
	21	* that an rbtree to find the service connection. Under ordinary circumstances
	22	* it might be slower than a large hash table, but it is at least limited in
	23	* depth.
	24	*/
	25	struct rxrpc_connection rxrpc_find_service_conn_rcu(struct rxrpc_peer peer,
	26	struct sk_buff *skb)
	27	{
	28	struct rxrpc_connection *conn = NULL;
	29	struct rxrpc_conn_proto k;
	30	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	31	struct rb_node *p;
	32	unsigned int seq = 0;
	33
	34	k.epoch = sp->hdr.epoch;
	35	k.cid = sp->hdr.cid & RXRPC_CIDMASK;
	36
	37	do {
	38	/* Unfortunately, rbtree walking doesn't give reliable results
	39	* under just the RCU read lock, so we have to check for
	40	* changes.
	41	*/
	42	read_seqbegin_or_lock(&peer->service_conn_lock, &seq);
	43
	44	p = rcu_dereference_raw(peer->service_conns.rb_node);
	45	while (p) {
	46	conn = rb_entry(p, struct rxrpc_connection, service_node);
	47
	48	if (conn->proto.index_key < k.index_key)
	49	p = rcu_dereference_raw(p->rb_left);
	50	else if (conn->proto.index_key > k.index_key)
	51	p = rcu_dereference_raw(p->rb_right);
	52	else
fdade4f6	53	break;
8496af50 DH	54	conn = NULL;
	55	}
	56	} while (need_seqretry(&peer->service_conn_lock, seq));
	57
8496af50 DH	58	done_seqretry(&peer->service_conn_lock, seq);
	59	_leave(" = %d", conn ? conn->debug_id : -1);
	60	return conn;
	61	}
	62
	63	/*
	64	* Insert a service connection into a peer's tree, thereby making it a target
	65	* for incoming packets.
	66	*/
248f219c DH	67	static void rxrpc_publish_service_conn(struct rxrpc_peer *peer,
248f219c DH	68	struct rxrpc_connection *conn)
8496af50 DH	69	{
	70	struct rxrpc_connection *cursor = NULL;
	71	struct rxrpc_conn_proto k = conn->proto;
	72	struct rb_node *pp, parent;
	73
	74	write_seqlock_bh(&peer->service_conn_lock);
	75
	76	pp = &peer->service_conns.rb_node;
	77	parent = NULL;
	78	while (*pp) {
	79	parent = *pp;
	80	cursor = rb_entry(parent,
	81	struct rxrpc_connection, service_node);
	82
	83	if (cursor->proto.index_key < k.index_key)
	84	pp = &(*pp)->rb_left;
	85	else if (cursor->proto.index_key > k.index_key)
	86	pp = &(*pp)->rb_right;
	87	else
	88	goto found_extant_conn;
	89	}
	90
	91	rb_link_node_rcu(&conn->service_node, parent, pp);
	92	rb_insert_color(&conn->service_node, &peer->service_conns);
	93	conn_published:
	94	set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags);
	95	write_sequnlock_bh(&peer->service_conn_lock);
	96	_leave(" = %d [new]", conn->debug_id);
248f219c	97	return;
8496af50 DH	98
	99	found_extant_conn:
	100	if (atomic_read(&cursor->usage) == 0)
	101	goto replace_old_connection;
	102	write_sequnlock_bh(&peer->service_conn_lock);
	103	/* We should not be able to get here. rxrpc_incoming_connection() is
	104	* called in a non-reentrant context, so there can't be a race to
	105	* insert a new connection.
	106	*/
	107	BUG();
	108
	109	replace_old_connection:
	110	/* The old connection is from an outdated epoch. */
	111	_debug("replace conn");
	112	rb_replace_node_rcu(&cursor->service_node,
	113	&conn->service_node,
	114	&peer->service_conns);
	115	clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags);
	116	goto conn_published;
	117	}
	118
00e90712 DH	119	/*
	120	* Preallocate a service connection. The connection is placed on the proc and
	121	* reap lists so that we don't have to get the lock from BH context.
	122	*/
2baec2c3 DH	123	struct rxrpc_connection rxrpc_prealloc_service_connection(struct rxrpc_net rxnet,
2baec2c3 DH	124	gfp_t gfp)
00e90712 DH	125	{
	126	struct rxrpc_connection *conn = rxrpc_alloc_connection(gfp);
	127
	128	if (conn) {
	129	/* We maintain an extra ref on the connection whilst it is on
	130	* the rxrpc_connections list.
	131	*/
	132	conn->state = RXRPC_CONN_SERVICE_PREALLOC;
	133	atomic_set(&conn->usage, 2);
	134
31f5f9a1	135	atomic_inc(&rxnet->nr_conns);
2baec2c3 DH	136	write_lock(&rxnet->conn_lock);
	137	list_add_tail(&conn->link, &rxnet->service_conns);
	138	list_add_tail(&conn->proc_link, &rxnet->conn_proc_list);
	139	write_unlock(&rxnet->conn_lock);
363deeab DH	140
	141	trace_rxrpc_conn(conn, rxrpc_conn_new_service,
	142	atomic_read(&conn->usage),
	143	__builtin_return_address(0));
00e90712 DH	144	}
	145
	146	return conn;
	147	}
	148
7877a4a4	149	/*
248f219c DH	150	* Set up an incoming connection. This is called in BH context with the RCU
248f219c DH	151	* read lock held.
7877a4a4	152	*/
4722974d DH	153	void rxrpc_new_incoming_connection(struct rxrpc_sock *rx,
4722974d DH	154	struct rxrpc_connection *conn,
248f219c	155	struct sk_buff *skb)
7877a4a4	156	{
7877a4a4	157	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
7877a4a4 DH	158
	159	_enter("");
	160
8496af50 DH	161	conn->proto.epoch = sp->hdr.epoch;
8496af50 DH	162	conn->proto.cid = sp->hdr.cid & RXRPC_CIDMASK;
8496af50	163	conn->params.service_id = sp->hdr.serviceId;
68d6d1ae	164	conn->service_id = sp->hdr.serviceId;
8496af50 DH	165	conn->security_ix = sp->hdr.securityIndex;
8496af50 DH	166	conn->out_clientflag = 0;
248f219c	167	if (conn->security_ix)
8496af50	168	conn->state = RXRPC_CONN_SERVICE_UNSECURED;
248f219c DH	169	else
248f219c DH	170	conn->state = RXRPC_CONN_SERVICE;
7877a4a4	171
4722974d DH	172	/* See if we should upgrade the service. This can only happen on the
	173	* first packet on a new connection. Once done, it applies to all
	174	* subsequent calls on that connection.
	175	*/
	176	if (sp->hdr.userStatus == RXRPC_USERSTATUS_SERVICE_UPGRADE &&
	177	conn->service_id == rx->service_upgrade.from)
	178	conn->service_id = rx->service_upgrade.to;
	179
8496af50	180	/* Make the connection a target for incoming packets. */
248f219c	181	rxrpc_publish_service_conn(conn->params.peer, conn);
8496af50	182
248f219c	183	_net("CONNECTION new %d {%x}", conn->debug_id, conn->proto.cid);
7877a4a4	184	}
001c1122 DH	185
	186	/*
	187	* Remove the service connection from the peer's tree, thereby removing it as a
	188	* target for incoming packets.
	189	*/
	190	void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn)
	191	{
	192	struct rxrpc_peer *peer = conn->params.peer;
	193
8496af50	194	write_seqlock_bh(&peer->service_conn_lock);
001c1122 DH	195	if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags))
001c1122 DH	196	rb_erase(&conn->service_node, &peer->service_conns);
8496af50	197	write_sequnlock_bh(&peer->service_conn_lock);
001c1122	198	}