From 42f229c350f57a8e825f7591e17cbc5c87e50235 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 6 Jan 2023 13:03:18 +0000 Subject: [PATCH] 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: 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: 5e6ef4f1017c ("rxrpc: Make the I/O thread take over the call and local processor work") Reported-by: Marc Dionne Signed-off-by: David Howells cc: linux-afs@lists.infradead.org --- net/rxrpc/af_rxrpc.c | 8 ++++---- net/rxrpc/ar-internal.h | 2 +- net/rxrpc/call_accept.c | 14 +++++++------- net/rxrpc/security.c | 6 +++--- 4 files changed, 15 insertions(+), 15 deletions(-) diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c index cf200e4..ebbd4a1 100644 --- a/net/rxrpc/af_rxrpc.c +++ b/net/rxrpc/af_rxrpc.c @@ -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); } diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 0072585..433060c 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -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 */ diff --git a/net/rxrpc/call_accept.c b/net/rxrpc/call_accept.c index 3fbf2fc..3e8689f 100644 --- a/net/rxrpc/call_accept.c +++ b/net/rxrpc/call_accept.c @@ -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; } diff --git a/net/rxrpc/security.c b/net/rxrpc/security.c index cd66634..cb8dd1d 100644 --- a/net/rxrpc/security.c +++ b/net/rxrpc/security.c @@ -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; } -- 2.7.4