tcp: handle inet_csk_reqsk_queue_add() failures

Commit 7716682cc58e ("tcp/dccp: fix another race at listener
dismantle") let inet_csk_reqsk_queue_add() fail, and adjusted
{tcp,dccp}_check_req() accordingly. However, TFO and syncookies
weren't modified, thus leaking allocated resources on error.

Contrary to tcp_check_req(), in both syncookies and TFO cases,
we need to drop the request socket. Also, since the child socket is
created with inet_csk_clone_lock(), we have to unlock it and drop an
extra reference (->sk_refcount is initially set to 2 and
inet_csk_reqsk_queue_add() drops only one ref).

For TFO, we also need to revert the work done by tcp_try_fastopen()
(with reqsk_fastopen_remove()).

Fixes: 7716682cc58e ("tcp/dccp: fix another race at listener dismantle")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 13 insertions, 2 deletions

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 606f868d9f3f..e531344611a0 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -216,7 +216,12 @@ struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
                 refcount_set(&req->rsk_refcnt, 1);
                 tcp_sk(child)->tsoffset = tsoff;
                 sock_rps_save_rxhash(child, skb);
-                inet_csk_reqsk_queue_add(sk, req, child);
+                if (!inet_csk_reqsk_queue_add(sk, req, child)) {
+                        bh_unlock_sock(child);
+                        sock_put(child);
+                        child = NULL;
+                        reqsk_put(req);
+                }
         } else {
                 reqsk_free(req);
         }
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4eb0c8ca3c60..5def3c48870e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6498,7 +6498,13 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
                 af_ops->send_synack(fastopen_sk, dst, &fl, req,
                                     &foc, TCP_SYNACK_FASTOPEN);
                 /* Add the child socket directly into the accept queue */
-                inet_csk_reqsk_queue_add(sk, req, fastopen_sk);
+                if (!inet_csk_reqsk_queue_add(sk, req, fastopen_sk)) {
+                        reqsk_fastopen_remove(fastopen_sk, req, false);
+                        bh_unlock_sock(fastopen_sk);
+                        sock_put(fastopen_sk);
+                        reqsk_put(req);
+                        goto drop;
+                }
                 sk->sk_data_ready(sk);
                 bh_unlock_sock(fastopen_sk);
                 sock_put(fastopen_sk);