linux/net/rxrpc/conn_object.c
David Howells 65550098c1 rxrpc: Fix race between recvmsg and sendmsg on immediate call failure
There's a race between rxrpc_sendmsg setting up a call, but then failing to
send anything on it due to an error, and recvmsg() seeing the call
completion occur and trying to return the state to the user.

An assertion fails in rxrpc_recvmsg() because the call has already been
released from the socket and is about to be released again as recvmsg deals
with it.  (The recvmsg_q queue on the socket holds a ref, so there's no
problem with use-after-free.)

We also have to be careful not to end up reporting an error twice, in such
a way that both returns indicate to userspace that the user ID supplied
with the call is no longer in use - which could cause the client to
malfunction if it recycles the user ID fast enough.

Fix this by the following means:

 (1) When sendmsg() creates a call after the point that the call has been
     successfully added to the socket, don't return any errors through
     sendmsg(), but rather complete the call and let recvmsg() retrieve
     them.  Make sendmsg() return 0 at this point.  Further calls to
     sendmsg() for that call will fail with ESHUTDOWN.

     Note that at this point, we haven't send any packets yet, so the
     server doesn't yet know about the call.

 (2) If sendmsg() returns an error when it was expected to create a new
     call, it means that the user ID wasn't used.

 (3) Mark the call disconnected before marking it completed to prevent an
     oops in rxrpc_release_call().

 (4) recvmsg() will then retrieve the error and set MSG_EOR to indicate
     that the user ID is no longer known by the kernel.

An oops like the following is produced:

	kernel BUG at net/rxrpc/recvmsg.c:605!
	...
	RIP: 0010:rxrpc_recvmsg+0x256/0x5ae
	...
	Call Trace:
	 ? __init_waitqueue_head+0x2f/0x2f
	 ____sys_recvmsg+0x8a/0x148
	 ? import_iovec+0x69/0x9c
	 ? copy_msghdr_from_user+0x5c/0x86
	 ___sys_recvmsg+0x72/0xaa
	 ? __fget_files+0x22/0x57
	 ? __fget_light+0x46/0x51
	 ? fdget+0x9/0x1b
	 do_recvmmsg+0x15e/0x232
	 ? _raw_spin_unlock+0xa/0xb
	 ? vtime_delta+0xf/0x25
	 __x64_sys_recvmmsg+0x2c/0x2f
	 do_syscall_64+0x4c/0x78
	 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 357f5ef646 ("rxrpc: Call rxrpc_release_call() on error in rxrpc_new_client_call()")
Reported-by: syzbot+b54969381df354936d96@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-07-30 16:50:20 -07:00

489 lines
13 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* RxRPC virtual connection handler, common bits.
*
* Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include "ar-internal.h"
/*
* Time till a connection expires after last use (in seconds).
*/
unsigned int __read_mostly rxrpc_connection_expiry = 10 * 60;
unsigned int __read_mostly rxrpc_closed_conn_expiry = 10;
static void rxrpc_destroy_connection(struct rcu_head *);
static void rxrpc_connection_timer(struct timer_list *timer)
{
struct rxrpc_connection *conn =
container_of(timer, struct rxrpc_connection, timer);
rxrpc_queue_conn(conn);
}
/*
* allocate a new connection
*/
struct rxrpc_connection *rxrpc_alloc_connection(gfp_t gfp)
{
struct rxrpc_connection *conn;
_enter("");
conn = kzalloc(sizeof(struct rxrpc_connection), gfp);
if (conn) {
INIT_LIST_HEAD(&conn->cache_link);
spin_lock_init(&conn->channel_lock);
INIT_LIST_HEAD(&conn->waiting_calls);
timer_setup(&conn->timer, &rxrpc_connection_timer, 0);
INIT_WORK(&conn->processor, &rxrpc_process_connection);
INIT_LIST_HEAD(&conn->proc_link);
INIT_LIST_HEAD(&conn->link);
skb_queue_head_init(&conn->rx_queue);
conn->security = &rxrpc_no_security;
spin_lock_init(&conn->state_lock);
conn->debug_id = atomic_inc_return(&rxrpc_debug_id);
conn->size_align = 4;
conn->idle_timestamp = jiffies;
}
_leave(" = %p{%d}", conn, conn ? conn->debug_id : 0);
return conn;
}
/*
* Look up a connection in the cache by protocol parameters.
*
* If successful, a pointer to the connection is returned, but no ref is taken.
* NULL is returned if there is no match.
*
* When searching for a service call, if we find a peer but no connection, we
* return that through *_peer in case we need to create a new service call.
*
* The caller must be holding the RCU read lock.
*/
struct rxrpc_connection *rxrpc_find_connection_rcu(struct rxrpc_local *local,
struct sk_buff *skb,
struct rxrpc_peer **_peer)
{
struct rxrpc_connection *conn;
struct rxrpc_conn_proto k;
struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
struct sockaddr_rxrpc srx;
struct rxrpc_peer *peer;
_enter(",%x", sp->hdr.cid & RXRPC_CIDMASK);
if (rxrpc_extract_addr_from_skb(&srx, skb) < 0)
goto not_found;
if (srx.transport.family != local->srx.transport.family &&
(srx.transport.family == AF_INET &&
local->srx.transport.family != AF_INET6)) {
pr_warn_ratelimited("AF_RXRPC: Protocol mismatch %u not %u\n",
srx.transport.family,
local->srx.transport.family);
goto not_found;
}
k.epoch = sp->hdr.epoch;
k.cid = sp->hdr.cid & RXRPC_CIDMASK;
if (rxrpc_to_server(sp)) {
/* We need to look up service connections by the full protocol
* parameter set. We look up the peer first as an intermediate
* step and then the connection from the peer's tree.
*/
peer = rxrpc_lookup_peer_rcu(local, &srx);
if (!peer)
goto not_found;
*_peer = peer;
conn = rxrpc_find_service_conn_rcu(peer, skb);
if (!conn || atomic_read(&conn->usage) == 0)
goto not_found;
_leave(" = %p", conn);
return conn;
} else {
/* Look up client connections by connection ID alone as their
* IDs are unique for this machine.
*/
conn = idr_find(&rxrpc_client_conn_ids,
sp->hdr.cid >> RXRPC_CIDSHIFT);
if (!conn || atomic_read(&conn->usage) == 0) {
_debug("no conn");
goto not_found;
}
if (conn->proto.epoch != k.epoch ||
conn->params.local != local)
goto not_found;
peer = conn->params.peer;
switch (srx.transport.family) {
case AF_INET:
if (peer->srx.transport.sin.sin_port !=
srx.transport.sin.sin_port ||
peer->srx.transport.sin.sin_addr.s_addr !=
srx.transport.sin.sin_addr.s_addr)
goto not_found;
break;
#ifdef CONFIG_AF_RXRPC_IPV6
case AF_INET6:
if (peer->srx.transport.sin6.sin6_port !=
srx.transport.sin6.sin6_port ||
memcmp(&peer->srx.transport.sin6.sin6_addr,
&srx.transport.sin6.sin6_addr,
sizeof(struct in6_addr)) != 0)
goto not_found;
break;
#endif
default:
BUG();
}
_leave(" = %p", conn);
return conn;
}
not_found:
_leave(" = NULL");
return NULL;
}
/*
* Disconnect a call and clear any channel it occupies when that call
* terminates. The caller must hold the channel_lock and must release the
* call's ref on the connection.
*/
void __rxrpc_disconnect_call(struct rxrpc_connection *conn,
struct rxrpc_call *call)
{
struct rxrpc_channel *chan =
&conn->channels[call->cid & RXRPC_CHANNELMASK];
_enter("%d,%x", conn->debug_id, call->cid);
if (rcu_access_pointer(chan->call) == call) {
/* Save the result of the call so that we can repeat it if necessary
* through the channel, whilst disposing of the actual call record.
*/
trace_rxrpc_disconnect_call(call);
switch (call->completion) {
case RXRPC_CALL_SUCCEEDED:
chan->last_seq = call->rx_hard_ack;
chan->last_type = RXRPC_PACKET_TYPE_ACK;
break;
case RXRPC_CALL_LOCALLY_ABORTED:
chan->last_abort = call->abort_code;
chan->last_type = RXRPC_PACKET_TYPE_ABORT;
break;
default:
chan->last_abort = RX_USER_ABORT;
chan->last_type = RXRPC_PACKET_TYPE_ABORT;
break;
}
/* Sync with rxrpc_conn_retransmit(). */
smp_wmb();
chan->last_call = chan->call_id;
chan->call_id = chan->call_counter;
rcu_assign_pointer(chan->call, NULL);
}
_leave("");
}
/*
* Disconnect a call and clear any channel it occupies when that call
* terminates.
*/
void rxrpc_disconnect_call(struct rxrpc_call *call)
{
struct rxrpc_connection *conn = call->conn;
call->peer->cong_cwnd = call->cong_cwnd;
if (!hlist_unhashed(&call->error_link)) {
spin_lock_bh(&call->peer->lock);
hlist_del_rcu(&call->error_link);
spin_unlock_bh(&call->peer->lock);
}
if (rxrpc_is_client_call(call))
return rxrpc_disconnect_client_call(call);
spin_lock(&conn->channel_lock);
__rxrpc_disconnect_call(conn, call);
spin_unlock(&conn->channel_lock);
set_bit(RXRPC_CALL_DISCONNECTED, &call->flags);
conn->idle_timestamp = jiffies;
}
/*
* Kill off a connection.
*/
void rxrpc_kill_connection(struct rxrpc_connection *conn)
{
struct rxrpc_net *rxnet = conn->params.local->rxnet;
ASSERT(!rcu_access_pointer(conn->channels[0].call) &&
!rcu_access_pointer(conn->channels[1].call) &&
!rcu_access_pointer(conn->channels[2].call) &&
!rcu_access_pointer(conn->channels[3].call));
ASSERT(list_empty(&conn->cache_link));
write_lock(&rxnet->conn_lock);
list_del_init(&conn->proc_link);
write_unlock(&rxnet->conn_lock);
/* Drain the Rx queue. Note that even though we've unpublished, an
* incoming packet could still be being added to our Rx queue, so we
* will need to drain it again in the RCU cleanup handler.
*/
rxrpc_purge_queue(&conn->rx_queue);
/* Leave final destruction to RCU. The connection processor work item
* must carry a ref on the connection to prevent us getting here whilst
* it is queued or running.
*/
call_rcu(&conn->rcu, rxrpc_destroy_connection);
}
/*
* Queue a connection's work processor, getting a ref to pass to the work
* queue.
*/
bool rxrpc_queue_conn(struct rxrpc_connection *conn)
{
const void *here = __builtin_return_address(0);
int n = atomic_fetch_add_unless(&conn->usage, 1, 0);
if (n == 0)
return false;
if (rxrpc_queue_work(&conn->processor))
trace_rxrpc_conn(conn->debug_id, rxrpc_conn_queued, n + 1, here);
else
rxrpc_put_connection(conn);
return true;
}
/*
* Note the re-emergence of a connection.
*/
void rxrpc_see_connection(struct rxrpc_connection *conn)
{
const void *here = __builtin_return_address(0);
if (conn) {
int n = atomic_read(&conn->usage);
trace_rxrpc_conn(conn->debug_id, rxrpc_conn_seen, n, here);
}
}
/*
* Get a ref on a connection.
*/
void rxrpc_get_connection(struct rxrpc_connection *conn)
{
const void *here = __builtin_return_address(0);
int n = atomic_inc_return(&conn->usage);
trace_rxrpc_conn(conn->debug_id, rxrpc_conn_got, n, here);
}
/*
* Try to get a ref on a connection.
*/
struct rxrpc_connection *
rxrpc_get_connection_maybe(struct rxrpc_connection *conn)
{
const void *here = __builtin_return_address(0);
if (conn) {
int n = atomic_fetch_add_unless(&conn->usage, 1, 0);
if (n > 0)
trace_rxrpc_conn(conn->debug_id, rxrpc_conn_got, n + 1, here);
else
conn = NULL;
}
return conn;
}
/*
* Set the service connection reap timer.
*/
static void rxrpc_set_service_reap_timer(struct rxrpc_net *rxnet,
unsigned long reap_at)
{
if (rxnet->live)
timer_reduce(&rxnet->service_conn_reap_timer, reap_at);
}
/*
* Release a service connection
*/
void rxrpc_put_service_conn(struct rxrpc_connection *conn)
{
const void *here = __builtin_return_address(0);
unsigned int debug_id = conn->debug_id;
int n;
n = atomic_dec_return(&conn->usage);
trace_rxrpc_conn(debug_id, rxrpc_conn_put_service, n, here);
ASSERTCMP(n, >=, 0);
if (n == 1)
rxrpc_set_service_reap_timer(conn->params.local->rxnet,
jiffies + rxrpc_connection_expiry);
}
/*
* destroy a virtual connection
*/
static void rxrpc_destroy_connection(struct rcu_head *rcu)
{
struct rxrpc_connection *conn =
container_of(rcu, struct rxrpc_connection, rcu);
_enter("{%d,u=%d}", conn->debug_id, atomic_read(&conn->usage));
ASSERTCMP(atomic_read(&conn->usage), ==, 0);
_net("DESTROY CONN %d", conn->debug_id);
del_timer_sync(&conn->timer);
rxrpc_purge_queue(&conn->rx_queue);
conn->security->clear(conn);
key_put(conn->params.key);
key_put(conn->server_key);
rxrpc_put_peer(conn->params.peer);
if (atomic_dec_and_test(&conn->params.local->rxnet->nr_conns))
wake_up_var(&conn->params.local->rxnet->nr_conns);
rxrpc_put_local(conn->params.local);
kfree(conn);
_leave("");
}
/*
* reap dead service connections
*/
void rxrpc_service_connection_reaper(struct work_struct *work)
{
struct rxrpc_connection *conn, *_p;
struct rxrpc_net *rxnet =
container_of(work, struct rxrpc_net, service_conn_reaper);
unsigned long expire_at, earliest, idle_timestamp, now;
LIST_HEAD(graveyard);
_enter("");
now = jiffies;
earliest = now + MAX_JIFFY_OFFSET;
write_lock(&rxnet->conn_lock);
list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
ASSERTCMP(atomic_read(&conn->usage), >, 0);
if (likely(atomic_read(&conn->usage) > 1))
continue;
if (conn->state == RXRPC_CONN_SERVICE_PREALLOC)
continue;
if (rxnet->live && !conn->params.local->dead) {
idle_timestamp = READ_ONCE(conn->idle_timestamp);
expire_at = idle_timestamp + rxrpc_connection_expiry * HZ;
if (conn->params.local->service_closed)
expire_at = idle_timestamp + rxrpc_closed_conn_expiry * HZ;
_debug("reap CONN %d { u=%d,t=%ld }",
conn->debug_id, atomic_read(&conn->usage),
(long)expire_at - (long)now);
if (time_before(now, expire_at)) {
if (time_before(expire_at, earliest))
earliest = expire_at;
continue;
}
}
/* The usage count sits at 1 whilst the object is unused on the
* list; we reduce that to 0 to make the object unavailable.
*/
if (atomic_cmpxchg(&conn->usage, 1, 0) != 1)
continue;
trace_rxrpc_conn(conn->debug_id, rxrpc_conn_reap_service, 0, NULL);
if (rxrpc_conn_is_client(conn))
BUG();
else
rxrpc_unpublish_service_conn(conn);
list_move_tail(&conn->link, &graveyard);
}
write_unlock(&rxnet->conn_lock);
if (earliest != now + MAX_JIFFY_OFFSET) {
_debug("reschedule reaper %ld", (long)earliest - (long)now);
ASSERT(time_after(earliest, now));
rxrpc_set_service_reap_timer(rxnet, earliest);
}
while (!list_empty(&graveyard)) {
conn = list_entry(graveyard.next, struct rxrpc_connection,
link);
list_del_init(&conn->link);
ASSERTCMP(atomic_read(&conn->usage), ==, 0);
rxrpc_kill_connection(conn);
}
_leave("");
}
/*
* preemptively destroy all the service connection records rather than
* waiting for them to time out
*/
void rxrpc_destroy_all_connections(struct rxrpc_net *rxnet)
{
struct rxrpc_connection *conn, *_p;
bool leak = false;
_enter("");
atomic_dec(&rxnet->nr_conns);
rxrpc_destroy_all_client_connections(rxnet);
del_timer_sync(&rxnet->service_conn_reap_timer);
rxrpc_queue_work(&rxnet->service_conn_reaper);
flush_workqueue(rxrpc_workqueue);
write_lock(&rxnet->conn_lock);
list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
pr_err("AF_RXRPC: Leaked conn %p {%d}\n",
conn, atomic_read(&conn->usage));
leak = true;
}
write_unlock(&rxnet->conn_lock);
BUG_ON(leak);
ASSERT(list_empty(&rxnet->conn_proc_list));
/* We need to wait for the connections to be destroyed by RCU as they
* pin things that we still need to get rid of.
*/
wait_var_event(&rxnet->nr_conns, !atomic_read(&rxnet->nr_conns));
_leave("");
}