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rxrpc: Fix incoming call setup race 

An incoming call can race with rxrpc socket destruction, leading to a
leaked call.  This may result in an oops when the call timer eventually
expires:

   BUG: kernel NULL pointer dereference, address: 0000000000000874
   RIP: 0010:_raw_spin_lock_irqsave+0x2a/0x50
   Call Trace:
    <IRQ>
    try_to_wake_up+0x59/0x550
    ? __local_bh_enable_ip+0x37/0x80
    ? rxrpc_poke_call+0x52/0x110 [rxrpc]
    ? rxrpc_poke_call+0x110/0x110 [rxrpc]
    ? rxrpc_poke_call+0x110/0x110 [rxrpc]
    call_timer_fn+0x24/0x120

with a warning in the kernel log looking something like:

   rxrpc: Call 00000000ba5e571a still in use (1,SvAwtACK,1061d,0)!

incurred during rmmod of rxrpc.  The 1061d is the call flags:

   RECVMSG_READ_ALL, RX_HEARD, BEGAN_RX_TIMER, RX_LAST, EXPOSED,
   IS_SERVICE, RELEASED

but no DISCONNECTED flag (0x800), so it's an incoming (service) call and
it's still connected.

The race appears to be that:

 (1) rxrpc_new_incoming_call() consults the service struct, checks sk_state
     and allocates a call - then pauses, possibly for an interrupt.

 (2) rxrpc_release_sock() sets RXRPC_CLOSE, nulls the service pointer,
     discards the prealloc and releases all calls attached to the socket.

 (3) rxrpc_new_incoming_call() resumes, launching the new call, including
     its timer and attaching it to the socket.

Fix this by read-locking local->services_lock to access the AF_RXRPC socket
providing the service rather than RCU in rxrpc_new_incoming_call().
There's no real need to use RCU here as local->services_lock is only
write-locked by the socket side in two places: when binding and when
shutting down.

Fixes: 5e6ef4f101 ("rxrpc: Make the I/O thread take over the call and local processor work")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
This commit is contained in:
David Howells 2023-01-06 13:03:18 +00:00
parent 9d35d880e0
commit 42f229c350
4 changed files with 15 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
net/rxrpc/af_rxrpc.c
View File

@ -155,10 +155,10 @@ static int rxrpc_bind(struct socket *sock, struct sockaddr *saddr, int len)
if (service_id) {
write_lock(&local->services_lock);
if (rcu_access_pointer(local->service))
if (local->service)
goto service_in_use;
rx->local = local;
rcu_assign_pointer(local->service, rx);
local->service = rx;
write_unlock(&local->services_lock);
rx->sk.sk_state = RXRPC_SERVER_BOUND;
@ -875,9 +875,9 @@ static int rxrpc_release_sock(struct sock *sk)
sk->sk_state = RXRPC_CLOSE;
if (rx->local && rcu_access_pointer(rx->local->service) == rx) {
if (rx->local && rx->local->service == rx) {
write_lock(&rx->local->services_lock);
rcu_assign_pointer(rx->local->service, NULL);
rx->local->service = NULL;
write_unlock(&rx->local->services_lock);
}

2
net/rxrpc/ar-internal.h
View File

@ -283,7 +283,7 @@ struct rxrpc_local {
struct socket *socket; /* my UDP socket */
struct task_struct *io_thread;
struct completion io_thread_ready; /* Indication that the I/O thread started */
struct rxrpc_sock __rcu *service; /* Service(s) listening on this endpoint */
struct rxrpc_sock *service; /* Service(s) listening on this endpoint */
struct rw_semaphore defrag_sem; /* control re-enablement of IP DF bit */
struct sk_buff_head rx_queue; /* Received packets */
struct list_head conn_attend_q; /* Conns requiring immediate attention */

14
net/rxrpc/call_accept.c
View File

@ -343,13 +343,13 @@ bool rxrpc_new_incoming_call(struct rxrpc_local *local,
if (sp->hdr.type != RXRPC_PACKET_TYPE_DATA)
return rxrpc_protocol_error(skb, rxrpc_eproto_no_service_call);
rcu_read_lock();
read_lock(&local->services_lock);
/* Weed out packets to services we're not offering. Packets that would
* begin a call are explicitly rejected and the rest are just
* discarded.
*/
rx = rcu_dereference(local->service);
rx = local->service;
if (!rx || (sp->hdr.serviceId != rx->srx.srx_service &&
sp->hdr.serviceId != rx->second_service)
) {
@ -399,7 +399,7 @@ bool rxrpc_new_incoming_call(struct rxrpc_local *local,
spin_unlock(&conn->state_lock);
spin_unlock(&rx->incoming_lock);
rcu_read_unlock();
read_unlock(&local->services_lock);
if (hlist_unhashed(&call->error_link)) {
spin_lock(&call->peer->lock);
@ -413,20 +413,20 @@ bool rxrpc_new_incoming_call(struct rxrpc_local *local,
return true;
unsupported_service:
rcu_read_unlock();
read_unlock(&local->services_lock);
return rxrpc_direct_abort(skb, rxrpc_abort_service_not_offered,
RX_INVALID_OPERATION, -EOPNOTSUPP);
unsupported_security:
rcu_read_unlock();
read_unlock(&local->services_lock);
return rxrpc_direct_abort(skb, rxrpc_abort_service_not_offered,
RX_INVALID_OPERATION, -EKEYREJECTED);
no_call:
spin_unlock(&rx->incoming_lock);
rcu_read_unlock();
read_unlock(&local->services_lock);
_leave(" = f [%u]", skb->mark);
return false;
discard:
rcu_read_unlock();
read_unlock(&local->services_lock);
return true;
}

6
net/rxrpc/security.c
View File

@ -178,9 +178,9 @@ struct key *rxrpc_look_up_server_security(struct rxrpc_connection *conn,
sprintf(kdesc, "%u:%u",
sp->hdr.serviceId, sp->hdr.securityIndex);
rcu_read_lock();
read_lock(&conn->local->services_lock);
rx = rcu_dereference(conn->local->service);
rx = conn->local->service;
if (!rx)
goto out;
@ -202,6 +202,6 @@ struct key *rxrpc_look_up_server_security(struct rxrpc_connection *conn,
}
out:
rcu_read_unlock();
read_unlock(&conn->local->services_lock);
return key;
}