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remarkable-linux/net/rxrpc/call_accept.c
David Howells 3432a757b1 rxrpc: Fix prealloc refcounting 
The preallocated call buffer holds a ref on the calls within that buffer.
The ref was being released in the wrong place - it worked okay for incoming
calls to the AFS cache manager service, but doesn't work right for incoming
calls to a userspace service.

Instead of releasing an extra ref service calls in rxrpc_release_call(),
the ref needs to be released during the acceptance/rejectance process.  To
this end:

 (1) The prealloc ref is now normally released during
     rxrpc_new_incoming_call().

 (2) For preallocated kernel API calls, the kernel API's ref needs to be
     released when the call is discarded on socket close.

 (3) We shouldn't take a second ref in rxrpc_accept_call().

 (4) rxrpc_recvmsg_new_call() needs to get a ref of its own when it adds
     the call to the to_be_accepted socket queue.

In doing (4) above, we would prefer not to put the call's refcount down to
0 as that entails doing cleanup in softirq context, but it's unlikely as
there are several refs held elsewhere, at least one of which must be put by
someone in process context calling rxrpc_release_call().  However, it's not
a problem if we do have to do that.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-09-13 22:38:37 +01:00

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/* incoming call handling
*
* Copyright (C) 2007 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 License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/errqueue.h>
#include <linux/udp.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/icmp.h>
#include <linux/gfp.h>
#include <linux/circ_buf.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <net/ip.h>
#include "ar-internal.h"
/*
* Preallocate a single service call, connection and peer and, if possible,
* give them a user ID and attach the user's side of the ID to them.
*/
static int rxrpc_service_prealloc_one(struct rxrpc_sock *rx,
struct rxrpc_backlog *b,
rxrpc_notify_rx_t notify_rx,
rxrpc_user_attach_call_t user_attach_call,
unsigned long user_call_ID, gfp_t gfp)
{
const void *here = __builtin_return_address(0);
struct rxrpc_call *call;
int max, tmp;
unsigned int size = RXRPC_BACKLOG_MAX;
unsigned int head, tail, call_head, call_tail;
max = rx->sk.sk_max_ack_backlog;
tmp = rx->sk.sk_ack_backlog;
if (tmp >= max) {
_leave(" = -ENOBUFS [full %u]", max);
return -ENOBUFS;
}
max -= tmp;
/* We don't need more conns and peers than we have calls, but on the
* other hand, we shouldn't ever use more peers than conns or conns
* than calls.
*/
call_head = b->call_backlog_head;
call_tail = READ_ONCE(b->call_backlog_tail);
tmp = CIRC_CNT(call_head, call_tail, size);
if (tmp >= max) {
_leave(" = -ENOBUFS [enough %u]", tmp);
return -ENOBUFS;
}
max = tmp + 1;
head = b->peer_backlog_head;
tail = READ_ONCE(b->peer_backlog_tail);
if (CIRC_CNT(head, tail, size) < max) {
struct rxrpc_peer *peer = rxrpc_alloc_peer(rx->local, gfp);
if (!peer)
return -ENOMEM;
b->peer_backlog[head] = peer;
smp_store_release(&b->peer_backlog_head,
(head + 1) & (size - 1));
}
head = b->conn_backlog_head;
tail = READ_ONCE(b->conn_backlog_tail);
if (CIRC_CNT(head, tail, size) < max) {
struct rxrpc_connection *conn;
conn = rxrpc_prealloc_service_connection(gfp);
if (!conn)
return -ENOMEM;
b->conn_backlog[head] = conn;
smp_store_release(&b->conn_backlog_head,
(head + 1) & (size - 1));
}
/* Now it gets complicated, because calls get registered with the
* socket here, particularly if a user ID is preassigned by the user.
*/
call = rxrpc_alloc_call(gfp);
if (!call)
return -ENOMEM;
call->flags |= (1 << RXRPC_CALL_IS_SERVICE);
call->state = RXRPC_CALL_SERVER_PREALLOC;
trace_rxrpc_call(call, rxrpc_call_new_service,
atomic_read(&call->usage),
here, (const void *)user_call_ID);
write_lock(&rx->call_lock);
if (user_attach_call) {
struct rxrpc_call *xcall;
struct rb_node *parent, **pp;
/* Check the user ID isn't already in use */
pp = &rx->calls.rb_node;
parent = NULL;
while (*pp) {
parent = *pp;
xcall = rb_entry(parent, struct rxrpc_call, sock_node);
if (user_call_ID < call->user_call_ID)
pp = &(*pp)->rb_left;
else if (user_call_ID > call->user_call_ID)
pp = &(*pp)->rb_right;
else
goto id_in_use;
}
call->user_call_ID = user_call_ID;
call->notify_rx = notify_rx;
rxrpc_get_call(call, rxrpc_call_got_kernel);
user_attach_call(call, user_call_ID);
rxrpc_get_call(call, rxrpc_call_got_userid);
rb_link_node(&call->sock_node, parent, pp);
rb_insert_color(&call->sock_node, &rx->calls);
set_bit(RXRPC_CALL_HAS_USERID, &call->flags);
}
list_add(&call->sock_link, &rx->sock_calls);
write_unlock(&rx->call_lock);
write_lock(&rxrpc_call_lock);
list_add_tail(&call->link, &rxrpc_calls);
write_unlock(&rxrpc_call_lock);
b->call_backlog[call_head] = call;
smp_store_release(&b->call_backlog_head, (call_head + 1) & (size - 1));
_leave(" = 0 [%d -> %lx]", call->debug_id, user_call_ID);
return 0;
id_in_use:
write_unlock(&rx->call_lock);
rxrpc_cleanup_call(call);
_leave(" = -EBADSLT");
return -EBADSLT;
}
/*
* Preallocate sufficient service connections, calls and peers to cover the
* entire backlog of a socket. When a new call comes in, if we don't have
* sufficient of each available, the call gets rejected as busy or ignored.
*
* The backlog is replenished when a connection is accepted or rejected.
*/
int rxrpc_service_prealloc(struct rxrpc_sock *rx, gfp_t gfp)
{
struct rxrpc_backlog *b = rx->backlog;
if (!b) {
b = kzalloc(sizeof(struct rxrpc_backlog), gfp);
if (!b)
return -ENOMEM;
rx->backlog = b;
}
if (rx->discard_new_call)
return 0;
while (rxrpc_service_prealloc_one(rx, b, NULL, NULL, 0, gfp) == 0)
;
return 0;
}
/*
* Discard the preallocation on a service.
*/
void rxrpc_discard_prealloc(struct rxrpc_sock *rx)
{
struct rxrpc_backlog *b = rx->backlog;
unsigned int size = RXRPC_BACKLOG_MAX, head, tail;
if (!b)
return;
rx->backlog = NULL;
/* Make sure that there aren't any incoming calls in progress before we
* clear the preallocation buffers.
*/
spin_lock_bh(&rx->incoming_lock);
spin_unlock_bh(&rx->incoming_lock);
head = b->peer_backlog_head;
tail = b->peer_backlog_tail;
while (CIRC_CNT(head, tail, size) > 0) {
struct rxrpc_peer *peer = b->peer_backlog[tail];
kfree(peer);
tail = (tail + 1) & (size - 1);
}
head = b->conn_backlog_head;
tail = b->conn_backlog_tail;
while (CIRC_CNT(head, tail, size) > 0) {
struct rxrpc_connection *conn = b->conn_backlog[tail];
write_lock(&rxrpc_connection_lock);
list_del(&conn->link);
list_del(&conn->proc_link);
write_unlock(&rxrpc_connection_lock);
kfree(conn);
tail = (tail + 1) & (size - 1);
}
head = b->call_backlog_head;
tail = b->call_backlog_tail;
while (CIRC_CNT(head, tail, size) > 0) {
struct rxrpc_call *call = b->call_backlog[tail];
if (rx->discard_new_call) {
_debug("discard %lx", call->user_call_ID);
rx->discard_new_call(call, call->user_call_ID);
rxrpc_put_call(call, rxrpc_call_put_kernel);
}
rxrpc_call_completed(call);
rxrpc_release_call(rx, call);
rxrpc_put_call(call, rxrpc_call_put);
tail = (tail + 1) & (size - 1);
}
kfree(b);
}
/*
* Allocate a new incoming call from the prealloc pool, along with a connection
* and a peer as necessary.
*/
static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx,
struct rxrpc_local *local,
struct rxrpc_connection *conn,
struct sk_buff *skb)
{
struct rxrpc_backlog *b = rx->backlog;
struct rxrpc_peer *peer, *xpeer;
struct rxrpc_call *call;
unsigned short call_head, conn_head, peer_head;
unsigned short call_tail, conn_tail, peer_tail;
unsigned short call_count, conn_count;
/* #calls >= #conns >= #peers must hold true. */
call_head = smp_load_acquire(&b->call_backlog_head);
call_tail = b->call_backlog_tail;
call_count = CIRC_CNT(call_head, call_tail, RXRPC_BACKLOG_MAX);
conn_head = smp_load_acquire(&b->conn_backlog_head);
conn_tail = b->conn_backlog_tail;
conn_count = CIRC_CNT(conn_head, conn_tail, RXRPC_BACKLOG_MAX);
ASSERTCMP(conn_count, >=, call_count);
peer_head = smp_load_acquire(&b->peer_backlog_head);
peer_tail = b->peer_backlog_tail;
ASSERTCMP(CIRC_CNT(peer_head, peer_tail, RXRPC_BACKLOG_MAX), >=,
conn_count);
if (call_count == 0)
return NULL;
if (!conn) {
/* No connection. We're going to need a peer to start off
* with. If one doesn't yet exist, use a spare from the
* preallocation set. We dump the address into the spare in
* anticipation - and to save on stack space.
*/
xpeer = b->peer_backlog[peer_tail];
if (rxrpc_extract_addr_from_skb(&xpeer->srx, skb) < 0)
return NULL;
peer = rxrpc_lookup_incoming_peer(local, xpeer);
if (peer == xpeer) {
b->peer_backlog[peer_tail] = NULL;
smp_store_release(&b->peer_backlog_tail,
(peer_tail + 1) &
(RXRPC_BACKLOG_MAX - 1));
}
/* Now allocate and set up the connection */
conn = b->conn_backlog[conn_tail];
b->conn_backlog[conn_tail] = NULL;
smp_store_release(&b->conn_backlog_tail,
(conn_tail + 1) & (RXRPC_BACKLOG_MAX - 1));
rxrpc_get_local(local);
conn->params.local = local;
conn->params.peer = peer;
rxrpc_new_incoming_connection(conn, skb);
} else {
rxrpc_get_connection(conn);
}
/* And now we can allocate and set up a new call */
call = b->call_backlog[call_tail];
b->call_backlog[call_tail] = NULL;
smp_store_release(&b->call_backlog_tail,
(call_tail + 1) & (RXRPC_BACKLOG_MAX - 1));
rxrpc_see_call(call);
call->conn = conn;
call->peer = rxrpc_get_peer(conn->params.peer);
return call;
}
/*
* Set up a new incoming call. Called in BH context with the RCU read lock
* held.
*
* If this is for a kernel service, when we allocate the call, it will have
* three refs on it: (1) the kernel service, (2) the user_call_ID tree, (3) the
* retainer ref obtained from the backlog buffer. Prealloc calls for userspace
* services only have the ref from the backlog buffer. We want to pass this
* ref to non-BH context to dispose of.
*
* If we want to report an error, we mark the skb with the packet type and
* abort code and return NULL.
*/
struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
struct rxrpc_connection *conn,
struct sk_buff *skb)
{
struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
struct rxrpc_sock *rx;
struct rxrpc_call *call;
_enter("");
/* Get the socket providing the service */
hlist_for_each_entry_rcu_bh(rx, &local->services, listen_link) {
if (rx->srx.srx_service == sp->hdr.serviceId)
goto found_service;
}
trace_rxrpc_abort("INV", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
RX_INVALID_OPERATION, EOPNOTSUPP);
skb->mark = RXRPC_SKB_MARK_LOCAL_ABORT;
skb->priority = RX_INVALID_OPERATION;
_leave(" = NULL [service]");
return NULL;
found_service:
spin_lock(&rx->incoming_lock);
if (rx->sk.sk_state == RXRPC_CLOSE) {
trace_rxrpc_abort("CLS", sp->hdr.cid, sp->hdr.callNumber,
sp->hdr.seq, RX_INVALID_OPERATION, ESHUTDOWN);
skb->mark = RXRPC_SKB_MARK_LOCAL_ABORT;
skb->priority = RX_INVALID_OPERATION;
_leave(" = NULL [close]");
call = NULL;
goto out;
}
call = rxrpc_alloc_incoming_call(rx, local, conn, skb);
if (!call) {
skb->mark = RXRPC_SKB_MARK_BUSY;
_leave(" = NULL [busy]");
call = NULL;
goto out;
}
/* Make the call live. */
rxrpc_incoming_call(rx, call, skb);
conn = call->conn;
if (rx->notify_new_call)
rx->notify_new_call(&rx->sk, call, call->user_call_ID);
spin_lock(&conn->state_lock);
switch (conn->state) {
case RXRPC_CONN_SERVICE_UNSECURED:
conn->state = RXRPC_CONN_SERVICE_CHALLENGING;
set_bit(RXRPC_CONN_EV_CHALLENGE, &call->conn->events);
rxrpc_queue_conn(call->conn);
break;
case RXRPC_CONN_SERVICE:
write_lock(&call->state_lock);
if (rx->discard_new_call)
call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
else
call->state = RXRPC_CALL_SERVER_ACCEPTING;
write_unlock(&call->state_lock);
break;
case RXRPC_CONN_REMOTELY_ABORTED:
rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
conn->remote_abort, ECONNABORTED);
break;
case RXRPC_CONN_LOCALLY_ABORTED:
rxrpc_abort_call("CON", call, sp->hdr.seq,
conn->local_abort, ECONNABORTED);
break;
default:
BUG();
}
spin_unlock(&conn->state_lock);
if (call->state == RXRPC_CALL_SERVER_ACCEPTING)
rxrpc_notify_socket(call);
/* We have to discard the prealloc queue's ref here and rely on a
* combination of the RCU read lock and refs held either by the socket
* (recvmsg queue, to-be-accepted queue or user ID tree) or the kernel
* service to prevent the call from being deallocated too early.
*/
rxrpc_put_call(call, rxrpc_call_put);
_leave(" = %p{%d}", call, call->debug_id);
out:
spin_unlock(&rx->incoming_lock);
return call;
}
/*
* handle acceptance of a call by userspace
* - assign the user call ID to the call at the front of the queue
*/
struct rxrpc_call *rxrpc_accept_call(struct rxrpc_sock *rx,
unsigned long user_call_ID,
rxrpc_notify_rx_t notify_rx)
{
struct rxrpc_call *call;
struct rb_node *parent, **pp;
int ret;
_enter(",%lx", user_call_ID);
ASSERT(!irqs_disabled());
write_lock(&rx->call_lock);
if (list_empty(&rx->to_be_accepted)) {
write_unlock(&rx->call_lock);
kleave(" = -ENODATA [empty]");
return ERR_PTR(-ENODATA);
}
/* check the user ID isn't already in use */
pp = &rx->calls.rb_node;
parent = NULL;
while (*pp) {
parent = *pp;
call = rb_entry(parent, struct rxrpc_call, sock_node);
if (user_call_ID < call->user_call_ID)
pp = &(*pp)->rb_left;
else if (user_call_ID > call->user_call_ID)
pp = &(*pp)->rb_right;
else
goto id_in_use;
}
/* Dequeue the first call and check it's still valid. We gain
* responsibility for the queue's reference.
*/
call = list_entry(rx->to_be_accepted.next,
struct rxrpc_call, accept_link);
list_del_init(&call->accept_link);
sk_acceptq_removed(&rx->sk);
rxrpc_see_call(call);
write_lock_bh(&call->state_lock);
switch (call->state) {
case RXRPC_CALL_SERVER_ACCEPTING:
call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
break;
case RXRPC_CALL_COMPLETE:
ret = call->error;
goto out_release;
default:
BUG();
}
/* formalise the acceptance */
call->notify_rx = notify_rx;
call->user_call_ID = user_call_ID;
rxrpc_get_call(call, rxrpc_call_got_userid);
rb_link_node(&call->sock_node, parent, pp);
rb_insert_color(&call->sock_node, &rx->calls);
if (test_and_set_bit(RXRPC_CALL_HAS_USERID, &call->flags))
BUG();
write_unlock_bh(&call->state_lock);
write_unlock(&rx->call_lock);
rxrpc_notify_socket(call);
rxrpc_service_prealloc(rx, GFP_KERNEL);
_leave(" = %p{%d}", call, call->debug_id);
return call;
out_release:
_debug("release %p", call);
write_unlock_bh(&call->state_lock);
write_unlock(&rx->call_lock);
rxrpc_release_call(rx, call);
rxrpc_put_call(call, rxrpc_call_put);
goto out;
id_in_use:
ret = -EBADSLT;
write_unlock(&rx->call_lock);
out:
rxrpc_service_prealloc(rx, GFP_KERNEL);
_leave(" = %d", ret);
return ERR_PTR(ret);
}
/*
* Handle rejection of a call by userspace
* - reject the call at the front of the queue
*/
int rxrpc_reject_call(struct rxrpc_sock *rx)
{
struct rxrpc_call *call;
bool abort = false;
int ret;
_enter("");
ASSERT(!irqs_disabled());
write_lock(&rx->call_lock);
if (list_empty(&rx->to_be_accepted)) {
write_unlock(&rx->call_lock);
return -ENODATA;
}
/* Dequeue the first call and check it's still valid. We gain
* responsibility for the queue's reference.
*/
call = list_entry(rx->to_be_accepted.next,
struct rxrpc_call, accept_link);
list_del_init(&call->accept_link);
sk_acceptq_removed(&rx->sk);
rxrpc_see_call(call);
write_lock_bh(&call->state_lock);
switch (call->state) {
case RXRPC_CALL_SERVER_ACCEPTING:
__rxrpc_abort_call("REJ", call, 1, RX_USER_ABORT, ECONNABORTED);
abort = true;
/* fall through */
case RXRPC_CALL_COMPLETE:
ret = call->error;
goto out_discard;
default:
BUG();
}
out_discard:
write_unlock_bh(&call->state_lock);
write_unlock(&rx->call_lock);
if (abort) {
rxrpc_send_call_packet(call, RXRPC_PACKET_TYPE_ABORT);
rxrpc_release_call(rx, call);
rxrpc_put_call(call, rxrpc_call_put);
}
rxrpc_service_prealloc(rx, GFP_KERNEL);
_leave(" = %d", ret);
return ret;
}
/*
* rxrpc_kernel_charge_accept - Charge up socket with preallocated calls
* @sock: The socket on which to preallocate
* @notify_rx: Event notification function for the call
* @user_attach_call: Func to attach call to user_call_ID
* @user_call_ID: The tag to attach to the preallocated call
* @gfp: The allocation conditions.
*
* Charge up the socket with preallocated calls, each with a user ID. A
* function should be provided to effect the attachment from the user's side.
* The user is given a ref to hold on the call.
*
* Note that the call may be come connected before this function returns.
*/
int rxrpc_kernel_charge_accept(struct socket *sock,
rxrpc_notify_rx_t notify_rx,
rxrpc_user_attach_call_t user_attach_call,
unsigned long user_call_ID, gfp_t gfp)
{
struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
struct rxrpc_backlog *b = rx->backlog;
if (sock->sk->sk_state == RXRPC_CLOSE)
return -ESHUTDOWN;
return rxrpc_service_prealloc_one(rx, b, notify_rx,
user_attach_call, user_call_ID,
gfp);
}
EXPORT_SYMBOL(rxrpc_kernel_charge_accept);
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