Merge: tcp: stable backports from upstream for 9.8 phase 2

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/7456

JIRA: https://issues.redhat.com/browse/RHEL-115628
CVE: CVE-2025-39955

A couple of fixes from upstream addressing critical issues, and a related follow-up

Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Approved-by: Florian Westphal <fwestpha@redhat.com>
Approved-by: Hangbin Liu <haliu@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

net/ipv4/tcp.c

@@ -3168,6 +3168,7 @@ int tcp_disconnect(struct sock *sk, int flags)
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 	int old_state = sk->sk_state;
+	struct request_sock *req;
 	u32 seq;
 
 	if (old_state != TCP_CLOSE)
@@ -3278,6 +3279,10 @@ int tcp_disconnect(struct sock *sk, int flags)
 
 
 	/* Clean up fastopen related fields */
+	req = rcu_dereference_protected(tp->fastopen_rsk,
+					lockdep_sock_is_held(sk));
+	if (req)
+		reqsk_fastopen_remove(sk, req, false);
 	tcp_free_fastopen_req(tp);
 	inet->defer_connect = 0;
 	tp->fastopen_client_fail = 0;

net/ipv4/tcp_input.c

@@ -7108,7 +7108,6 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 				    &foc, TCP_SYNACK_FASTOPEN, skb);
 		/* Add the child socket directly into the accept queue */
 		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);
 			goto drop_and_free;

net/ipv4/tcp_output.c

@@ -828,8 +828,10 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
 		unsigned int size;
 
 		if (mptcp_syn_options(sk, skb, &size, &opts->mptcp)) {
-			opts->options |= OPTION_MPTCP;
-			remaining -= size;
+			if (remaining >= size) {
+				opts->options |= OPTION_MPTCP;
+				remaining -= size;
+			}
 		}
 	}