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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 2 insertions, 26 deletions

diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index e84ea9f2498f..63615709839d 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -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);
 
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index 2e73748956d5..a0dde04eb178 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -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)
 {