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Commit ebb516af authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp/dccp: fix race at listener dismantle phase 



Under stress, a close() on a listener can trigger the
WARN_ON(sk->sk_ack_backlog) in inet_csk_listen_stop()

We need to test if listener is still active before queueing
a child in inet_csk_reqsk_queue_add()

Create a common inet_child_forget() helper, and use it
from inet_csk_reqsk_queue_add() and inet_csk_listen_stop()

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f03f2e15

include/net/inet_connection_sock.h

+2 −7
Original line number Diff line number Diff line
@@ -268,13 +268,8 @@ struct dst_entry *inet_csk_route_child_sock(const struct sock *sk, 
					    struct sock *newsk,

					    const struct request_sock *req);



static inline void inet_csk_reqsk_queue_add(struct sock *sk,

					    struct request_sock *req,

					    struct sock *child)

{

	reqsk_queue_add(&inet_csk(sk)->icsk_accept_queue, req, sk, child);

}



void inet_csk_reqsk_queue_add(struct sock *sk, struct request_sock *req,

			      struct sock *child);

void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,

				   unsigned long timeout);

include/net/request_sock.h

+0 −19
Original line number Diff line number Diff line
@@ -186,25 +186,6 @@ static inline bool reqsk_queue_empty(const struct request_sock_queue *queue) 
	return queue->rskq_accept_head == NULL;

}



static inline void reqsk_queue_add(struct request_sock_queue *queue,

				   struct request_sock *req,

				   struct sock *parent,

				   struct sock *child)

{

	spin_lock(&queue->rskq_lock);

	req->sk = child;

	sk_acceptq_added(parent);



	if (queue->rskq_accept_head == NULL)

		queue->rskq_accept_head = req;

	else

		queue->rskq_accept_tail->dl_next = req;



	queue->rskq_accept_tail = req;

	req->dl_next = NULL;

	spin_unlock(&queue->rskq_lock);

}



static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,

						      struct sock *parent)

{

net/ipv4/inet_connection_sock.c

+49 −22
Original line number Diff line number Diff line
@@ -764,6 +764,53 @@ int inet_csk_listen_start(struct sock *sk, int backlog) 
}

EXPORT_SYMBOL_GPL(inet_csk_listen_start);



static void inet_child_forget(struct sock *sk, struct request_sock *req,

			      struct sock *child)

{

	sk->sk_prot->disconnect(child, O_NONBLOCK);



	sock_orphan(child);



	percpu_counter_inc(sk->sk_prot->orphan_count);



	if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(req)->tfo_listener) {

		BUG_ON(tcp_sk(child)->fastopen_rsk != req);

		BUG_ON(sk != req->rsk_listener);



		/* Paranoid, to prevent race condition if

		 * an inbound pkt destined for child is

		 * blocked by sock lock in tcp_v4_rcv().

		 * Also to satisfy an assertion in

		 * tcp_v4_destroy_sock().

		 */

		tcp_sk(child)->fastopen_rsk = NULL;

	}

	inet_csk_destroy_sock(child);

	reqsk_put(req);

}



void inet_csk_reqsk_queue_add(struct sock *sk, struct request_sock *req,

			      struct sock *child)

{

	struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;



	spin_lock(&queue->rskq_lock);

	if (unlikely(sk->sk_state != TCP_LISTEN)) {

		inet_child_forget(sk, req, child);

	} else {

		req->sk = child;

		req->dl_next = NULL;

		if (queue->rskq_accept_head == NULL)

			queue->rskq_accept_head = req;

		else

			queue->rskq_accept_tail->dl_next = req;

		queue->rskq_accept_tail = req;

		sk_acceptq_added(sk);

	}

	spin_unlock(&queue->rskq_lock);

}

EXPORT_SYMBOL(inet_csk_reqsk_queue_add);



/*

 *	This routine closes sockets which have been at least partially

 *	opened, but not yet accepted.
@@ -790,31 +837,11 @@ void inet_csk_listen_stop(struct sock *sk) 
		WARN_ON(sock_owned_by_user(child));

		sock_hold(child);



		sk->sk_prot->disconnect(child, O_NONBLOCK);



		sock_orphan(child);



		percpu_counter_inc(sk->sk_prot->orphan_count);



		if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(req)->tfo_listener) {

			BUG_ON(tcp_sk(child)->fastopen_rsk != req);

			BUG_ON(sk != req->rsk_listener);



			/* Paranoid, to prevent race condition if

			 * an inbound pkt destined for child is

			 * blocked by sock lock in tcp_v4_rcv().

			 * Also to satisfy an assertion in

			 * tcp_v4_destroy_sock().

			 */

			tcp_sk(child)->fastopen_rsk = NULL;

		}

		inet_csk_destroy_sock(child);



		inet_child_forget(sk, req, child);

		bh_unlock_sock(child);

		local_bh_enable();

		sock_put(child);



		reqsk_put(req);

		cond_resched();

	}

	if (queue->fastopenq.rskq_rst_head) {
@@ -829,7 +856,7 @@ void inet_csk_listen_stop(struct sock *sk) 
			req = next;

		}

	}

	WARN_ON(sk->sk_ack_backlog);

	WARN_ON_ONCE(sk->sk_ack_backlog);

}

EXPORT_SYMBOL_GPL(inet_csk_listen_stop);