Merge tag 'rxrpc-fixes-20230107' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

David Howells says:

====================
rxrpc: Fix race between call connection, data transmit and call disconnect

Here are patches to fix an oops[1] caused by a race between call
connection, initial packet transmission and call disconnection which
results in something like:

        kernel BUG at net/rxrpc/peer_object.c:413!

when the syzbot test is run.  The problem is that the connection procedure
is effectively split across two threads and can get expanded by taking an
interrupt, thereby adding the call to the peer error distribution list
*after* it has been disconnected (say by the rxrpc socket shutting down).

The easiest solution is to look at the fourth set of I/O thread
conversion/SACK table expansion patches that didn't get applied[2] and take
from it those patches that move call connection and disconnection into the
I/O thread.  Moving these things into the I/O thread means that the
sequencing is managed by all being done in the same thread - and the race
can no longer happen.

This is preferable to introducing an extra lock as adding an extra lock
would make the I/O thread have to wait for the app thread in yet another
place.

The changes can be considered as a number of logical parts:

 (1) Move all of the call state changes into the I/O thread.

 (2) Make client connection ID space per-local endpoint so that the I/O
     thread doesn't need locks to access it.

 (3) Move actual abort generation into the I/O thread and clean it up.  If
     sendmsg or recvmsg want to cause an abort, they have to delegate it.

 (4) Offload the setting up of the security context on a connection to the
     thread of one of the apps that's starting a call.  We don't want to be
     doing any sort of crypto in the I/O thread.

 (5) Connect calls (ie. assign them to channel slots on connections) in the
     I/O thread.  Calls are set up by sendmsg/kafs and passed to the I/O
     thread to connect.  Connections are allocated in the I/O thread after
     this.

 (6) Disconnect calls in the I/O thread.

I've also added a patch for an unrelated bug that cropped up during
testing, whereby a race can occur between an incoming call and socket
shutdown.

Note that whilst this fixes the original syzbot bug, another bug may get
triggered if this one is fixed:

        INFO: rcu detected stall in corrupted
        rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { P5792 } 2657 jiffies s: 2825 root: 0x0/T
        rcu: blocking rcu_node structures (internal RCU debug):

It doesn't look this should be anything to do with rxrpc, though, as I've
tested an additional patch[3] that removes practically all the RCU usage
from rxrpc and it still occurs.  It seems likely that it is being caused by
something in the tunnelling setup that the syzbot test does, but there's
not enough info to go on.  It also seems unlikely to be anything to do with
the afs driver as the test doesn't use that.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 109 insertions, 95 deletions

diff --git a/net/rxrpc/io_thread.c b/net/rxrpc/io_thread.c
index 1ad067d66fb60..9e9dfb2fc559b 100644
--- a/net/rxrpc/io_thread.c
+++ b/net/rxrpc/io_thread.c
@@ -67,9 +67,31 @@ void rxrpc_error_report(struct sock *sk)
 }
 
 /*
+ * Directly produce an abort from a packet.
+ */
+bool rxrpc_direct_abort(struct sk_buff *skb, enum rxrpc_abort_reason why,
+			s32 abort_code, int err)
+{
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+
+	trace_rxrpc_abort(0, why, sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
+			  abort_code, err);
+	skb->mark = RXRPC_SKB_MARK_REJECT_ABORT;
+	skb->priority = abort_code;
+	return false;
+}
+
+static bool rxrpc_bad_message(struct sk_buff *skb, enum rxrpc_abort_reason why)
+{
+	return rxrpc_direct_abort(skb, why, RX_PROTOCOL_ERROR, -EBADMSG);
+}
+
+#define just_discard true
+
+/*
  * Process event packets targeted at a local endpoint.
  */
-static void rxrpc_input_version(struct rxrpc_local *local, struct sk_buff *skb)
+static bool rxrpc_input_version(struct rxrpc_local *local, struct sk_buff *skb)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	char v;
@@ -81,22 +103,21 @@ static void rxrpc_input_version(struct rxrpc_local *local, struct sk_buff *skb)
 		if (v == 0)
 			rxrpc_send_version_request(local, &sp->hdr, skb);
 	}
+
+	return true;
 }
 
 /*
  * Extract the wire header from a packet and translate the byte order.
  */
-static noinline
-int rxrpc_extract_header(struct rxrpc_skb_priv *sp, struct sk_buff *skb)
+static bool rxrpc_extract_header(struct rxrpc_skb_priv *sp,
+				 struct sk_buff *skb)
 {
 	struct rxrpc_wire_header whdr;
 
 	/* dig out the RxRPC connection details */
-	if (skb_copy_bits(skb, 0, &whdr, sizeof(whdr)) < 0) {
-		trace_rxrpc_rx_eproto(NULL, sp->hdr.serial,
-				      tracepoint_string("bad_hdr"));
-		return -EBADMSG;
-	}
+	if (skb_copy_bits(skb, 0, &whdr, sizeof(whdr)) < 0)
+		return rxrpc_bad_message(skb, rxrpc_badmsg_short_hdr);
 
 	memset(sp, 0, sizeof(*sp));
 	sp->hdr.epoch		= ntohl(whdr.epoch);
@@ -110,7 +131,7 @@ int rxrpc_extract_header(struct rxrpc_skb_priv *sp, struct sk_buff *skb)
 	sp->hdr.securityIndex	= whdr.securityIndex;
 	sp->hdr._rsvd		= ntohs(whdr._rsvd);
 	sp->hdr.serviceId	= ntohs(whdr.serviceId);
-	return 0;
+	return true;
 }
 
 /*
@@ -130,28 +151,28 @@ static bool rxrpc_extract_abort(struct sk_buff *skb)
 /*
  * Process packets received on the local endpoint
  */
-static int rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb)
+static bool rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb)
 {
 	struct rxrpc_connection *conn;
 	struct sockaddr_rxrpc peer_srx;
 	struct rxrpc_skb_priv *sp;
 	struct rxrpc_peer *peer = NULL;
 	struct sk_buff *skb = *_skb;
-	int ret = 0;
+	bool ret = false;
 
 	skb_pull(skb, sizeof(struct udphdr));
 
 	sp = rxrpc_skb(skb);
 
 	/* dig out the RxRPC connection details */
-	if (rxrpc_extract_header(sp, skb) < 0)
-		goto bad_message;
+	if (!rxrpc_extract_header(sp, skb))
+		return just_discard;
 
 	if (IS_ENABLED(CONFIG_AF_RXRPC_INJECT_LOSS)) {
 		static int lose;
 		if ((lose++ & 7) == 7) {
 			trace_rxrpc_rx_lose(sp);
-			return 0;
+			return just_discard;
 		}
 	}
 
@@ -160,28 +181,28 @@ static int rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb)
 	switch (sp->hdr.type) {
 	case RXRPC_PACKET_TYPE_VERSION:
 		if (rxrpc_to_client(sp))
-			return 0;
-		rxrpc_input_version(local, skb);
-		return 0;
+			return just_discard;
+		return rxrpc_input_version(local, skb);
 
 	case RXRPC_PACKET_TYPE_BUSY:
 		if (rxrpc_to_server(sp))
-			return 0;
+			return just_discard;
 		fallthrough;
 	case RXRPC_PACKET_TYPE_ACK:
 	case RXRPC_PACKET_TYPE_ACKALL:
 		if (sp->hdr.callNumber == 0)
-			goto bad_message;
+			return rxrpc_bad_message(skb, rxrpc_badmsg_zero_call);
 		break;
 	case RXRPC_PACKET_TYPE_ABORT:
 		if (!rxrpc_extract_abort(skb))
-			return 0; /* Just discard if malformed */
+			return just_discard; /* Just discard if malformed */
 		break;
 
 	case RXRPC_PACKET_TYPE_DATA:
-		if (sp->hdr.callNumber == 0 ||
-		    sp->hdr.seq == 0)
-			goto bad_message;
+		if (sp->hdr.callNumber == 0)
+			return rxrpc_bad_message(skb, rxrpc_badmsg_zero_call);
+		if (sp->hdr.seq == 0)
+			return rxrpc_bad_message(skb, rxrpc_badmsg_zero_seq);
 
 		/* Unshare the packet so that it can be modified for in-place
 		 * decryption.
@@ -191,7 +212,7 @@ static int rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb)
 			if (!skb) {
 				rxrpc_eaten_skb(*_skb, rxrpc_skb_eaten_by_unshare_nomem);
 				*_skb = NULL;
-				return 0;
+				return just_discard;
 			}
 
 			if (skb != *_skb) {
@@ -205,28 +226,28 @@ static int rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb)
 
 	case RXRPC_PACKET_TYPE_CHALLENGE:
 		if (rxrpc_to_server(sp))
-			return 0;
+			return just_discard;
 		break;
 	case RXRPC_PACKET_TYPE_RESPONSE:
 		if (rxrpc_to_client(sp))
-			return 0;
+			return just_discard;
 		break;
 
 		/* Packet types 9-11 should just be ignored. */
 	case RXRPC_PACKET_TYPE_PARAMS:
 	case RXRPC_PACKET_TYPE_10:
 	case RXRPC_PACKET_TYPE_11:
-		return 0;
+		return just_discard;
 
 	default:
-		goto bad_message;
+		return rxrpc_bad_message(skb, rxrpc_badmsg_unsupported_packet);
 	}
 
 	if (sp->hdr.serviceId == 0)
-		goto bad_message;
+		return rxrpc_bad_message(skb, rxrpc_badmsg_zero_service);
 
 	if (WARN_ON_ONCE(rxrpc_extract_addr_from_skb(&peer_srx, skb) < 0))
-		return true; /* Unsupported address type - discard. */
+		return just_discard; /* Unsupported address type. */
 
 	if (peer_srx.transport.family != local->srx.transport.family &&
 	    (peer_srx.transport.family == AF_INET &&
@@ -234,7 +255,7 @@ static int rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb)
 		pr_warn_ratelimited("AF_RXRPC: Protocol mismatch %u not %u\n",
 				    peer_srx.transport.family,
 				    local->srx.transport.family);
-		return true; /* Wrong address type - discard. */
+		return just_discard; /* Wrong address type. */
 	}
 
 	if (rxrpc_to_client(sp)) {
@@ -242,12 +263,8 @@ static int rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb)
 		conn = rxrpc_find_client_connection_rcu(local, &peer_srx, skb);
 		conn = rxrpc_get_connection_maybe(conn, rxrpc_conn_get_call_input);
 		rcu_read_unlock();
-		if (!conn) {
-			trace_rxrpc_abort(0, "NCC", sp->hdr.cid,
-					  sp->hdr.callNumber, sp->hdr.seq,
-					  RXKADINCONSISTENCY, EBADMSG);
-			goto protocol_error;
-		}
+		if (!conn)
+			return rxrpc_protocol_error(skb, rxrpc_eproto_no_client_conn);
 
 		ret = rxrpc_input_packet_on_conn(conn, &peer_srx, skb);
 		rxrpc_put_connection(conn, rxrpc_conn_put_call_input);
@@ -280,19 +297,7 @@ static int rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb)
 
 	ret = rxrpc_new_incoming_call(local, peer, NULL, &peer_srx, skb);
 	rxrpc_put_peer(peer, rxrpc_peer_put_input);
-	if (ret < 0)
-		goto reject_packet;
-	return 0;
-
-bad_message:
-	trace_rxrpc_abort(0, "BAD", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
-			  RX_PROTOCOL_ERROR, EBADMSG);
-protocol_error:
-	skb->priority = RX_PROTOCOL_ERROR;
-	skb->mark = RXRPC_SKB_MARK_REJECT_ABORT;
-reject_packet:
-	rxrpc_reject_packet(local, skb);
-	return 0;
+	return ret;
 }
 
 /*
@@ -306,21 +311,23 @@ static int rxrpc_input_packet_on_conn(struct rxrpc_connection *conn,
 	struct rxrpc_channel *chan;
 	struct rxrpc_call *call = NULL;
 	unsigned int channel;
+	bool ret;
 
 	if (sp->hdr.securityIndex != conn->security_ix)
-		goto wrong_security;
+		return rxrpc_direct_abort(skb, rxrpc_eproto_wrong_security,
+					  RXKADINCONSISTENCY, -EBADMSG);
 
 	if (sp->hdr.serviceId != conn->service_id) {
 		int old_id;
 
 		if (!test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags))
-			goto reupgrade;
+			return rxrpc_protocol_error(skb, rxrpc_eproto_reupgrade);
+
 		old_id = cmpxchg(&conn->service_id, conn->orig_service_id,
 				 sp->hdr.serviceId);
-
 		if (old_id != conn->orig_service_id &&
 		    old_id != sp->hdr.serviceId)
-			goto reupgrade;
+			return rxrpc_protocol_error(skb, rxrpc_eproto_bad_upgrade);
 	}
 
 	if (after(sp->hdr.serial, conn->hi_serial))
@@ -336,19 +343,19 @@ static int rxrpc_input_packet_on_conn(struct rxrpc_connection *conn,
 
 	/* Ignore really old calls */
 	if (sp->hdr.callNumber < chan->last_call)
-		return 0;
+		return just_discard;
 
 	if (sp->hdr.callNumber == chan->last_call) {
 		if (chan->call ||
 		    sp->hdr.type == RXRPC_PACKET_TYPE_ABORT)
-			return 0;
+			return just_discard;
 
 		/* For the previous service call, if completed successfully, we
 		 * discard all further packets.
 		 */
 		if (rxrpc_conn_is_service(conn) &&
 		    chan->last_type == RXRPC_PACKET_TYPE_ACK)
-			return 0;
+			return just_discard;
 
 		/* But otherwise we need to retransmit the final packet from
 		 * data cached in the connection record.
@@ -358,19 +365,17 @@ static int rxrpc_input_packet_on_conn(struct rxrpc_connection *conn,
 					    sp->hdr.seq,
 					    sp->hdr.serial,
 					    sp->hdr.flags);
-		rxrpc_input_conn_packet(conn, skb);
-		return 0;
+		rxrpc_conn_retransmit_call(conn, skb, channel);
+		return just_discard;
 	}
 
-	rcu_read_lock();
-	call = rxrpc_try_get_call(rcu_dereference(chan->call),
-				  rxrpc_call_get_input);
-	rcu_read_unlock();
+	call = rxrpc_try_get_call(chan->call, rxrpc_call_get_input);
 
 	if (sp->hdr.callNumber > chan->call_id) {
 		if (rxrpc_to_client(sp)) {
 			rxrpc_put_call(call, rxrpc_call_put_input);
-			goto reject_packet;
+			return rxrpc_protocol_error(skb,
+						    rxrpc_eproto_unexpected_implicit_end);
 		}
 
 		if (call) {
@@ -382,38 +387,14 @@ static int rxrpc_input_packet_on_conn(struct rxrpc_connection *conn,
 
 	if (!call) {
 		if (rxrpc_to_client(sp))
-			goto bad_message;
-		if (rxrpc_new_incoming_call(conn->local, conn->peer, conn,
-					    peer_srx, skb) == 0)
-			return 0;
-		goto reject_packet;
+			return rxrpc_protocol_error(skb, rxrpc_eproto_no_client_call);
+		return rxrpc_new_incoming_call(conn->local, conn->peer, conn,
+					       peer_srx, skb);
 	}
 
-	rxrpc_input_call_event(call, skb);
+	ret = rxrpc_input_call_event(call, skb);
 	rxrpc_put_call(call, rxrpc_call_put_input);
-	return 0;
-
-wrong_security:
-	trace_rxrpc_abort(0, "SEC", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
-			  RXKADINCONSISTENCY, EBADMSG);
-	skb->priority = RXKADINCONSISTENCY;
-	goto post_abort;
-
-reupgrade:
-	trace_rxrpc_abort(0, "UPG", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
-			  RX_PROTOCOL_ERROR, EBADMSG);
-	goto protocol_error;
-
-bad_message:
-	trace_rxrpc_abort(0, "BAD", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
-			  RX_PROTOCOL_ERROR, EBADMSG);
-protocol_error:
-	skb->priority = RX_PROTOCOL_ERROR;
-post_abort:
-	skb->mark = RXRPC_SKB_MARK_REJECT_ABORT;
-reject_packet:
-	rxrpc_reject_packet(conn->local, skb);
-	return 0;
+	return ret;
 }
 
 /*
@@ -421,6 +402,7 @@ reject_packet:
  */
 int rxrpc_io_thread(void *data)
 {
+	struct rxrpc_connection *conn;
 	struct sk_buff_head rx_queue;
 	struct rxrpc_local *local = data;
 	struct rxrpc_call *call;
@@ -436,6 +418,24 @@ int rxrpc_io_thread(void *data)
 	for (;;) {
 		rxrpc_inc_stat(local->rxnet, stat_io_loop);
 
+		/* Deal with connections that want immediate attention. */
+		conn = list_first_entry_or_null(&local->conn_attend_q,
+						struct rxrpc_connection,
+						attend_link);
+		if (conn) {
+			spin_lock_bh(&local->lock);
+			list_del_init(&conn->attend_link);
+			spin_unlock_bh(&local->lock);
+
+			rxrpc_input_conn_event(conn, NULL);
+			rxrpc_put_connection(conn, rxrpc_conn_put_poke);
+			continue;
+		}
+
+		if (test_and_clear_bit(RXRPC_CLIENT_CONN_REAP_TIMER,
+				       &local->client_conn_flags))
+			rxrpc_discard_expired_client_conns(local);
+
 		/* Deal with calls that want immediate attention. */
 		if ((call = list_first_entry_or_null(&local->call_attend_q,
 						     struct rxrpc_call,
@@ -450,12 +450,17 @@ int rxrpc_io_thread(void *data)
 			continue;
 		}
 
+		if (!list_empty(&local->new_client_calls))
+			rxrpc_connect_client_calls(local);
+
 		/* Process received packets and errors. */
 		if ((skb = __skb_dequeue(&rx_queue))) {
+			struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 			switch (skb->mark) {
 			case RXRPC_SKB_MARK_PACKET:
 				skb->priority = 0;
-				rxrpc_input_packet(local, &skb);
+				if (!rxrpc_input_packet(local, &skb))
+					rxrpc_reject_packet(local, skb);
 				trace_rxrpc_rx_done(skb->mark, skb->priority);
 				rxrpc_free_skb(skb, rxrpc_skb_put_input);
 				break;
@@ -463,6 +468,11 @@ int rxrpc_io_thread(void *data)
 				rxrpc_input_error(local, skb);
 				rxrpc_free_skb(skb, rxrpc_skb_put_error_report);
 				break;
+			case RXRPC_SKB_MARK_SERVICE_CONN_SECURED:
+				rxrpc_input_conn_event(sp->conn, skb);
+				rxrpc_put_connection(sp->conn, rxrpc_conn_put_poke);
+				rxrpc_free_skb(skb, rxrpc_skb_put_conn_secured);
+				break;
 			default:
 				WARN_ON_ONCE(1);
 				rxrpc_free_skb(skb, rxrpc_skb_put_unknown);
@@ -481,7 +491,11 @@ int rxrpc_io_thread(void *data)
 		set_current_state(TASK_INTERRUPTIBLE);
 		should_stop = kthread_should_stop();
 		if (!skb_queue_empty(&local->rx_queue) ||
-		    !list_empty(&local->call_attend_q)) {
+		    !list_empty(&local->call_attend_q) ||
+		    !list_empty(&local->conn_attend_q) ||
+		    !list_empty(&local->new_client_calls) ||
+		    test_bit(RXRPC_CLIENT_CONN_REAP_TIMER,
+			     &local->client_conn_flags)) {
 			__set_current_state(TASK_RUNNING);
 			continue;
 		}