FAILED: patch "[PATCH] mptcp: fix more tx path fields initialization" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 3f83d8a77eeeb47011b990fd766a421ee64f1d73
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024021910-cold-outmost-b825@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

3f83d8a77eee ("mptcp: fix more tx path fields initialization") 013e3179dbd2 ("mptcp: fix rcv space initialization") c693a8516429 ("mptcp: use mptcp_set_state")
4fd19a307016 ("mptcp: fix inconsistent state on fastopen race") d109a7767273 ("mptcp: fix possible NULL pointer dereference on close") 8005184fd1ca ("mptcp: refactor sndbuf auto-tuning")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3f83d8a77eeeb47011b990fd766a421ee64f1d73 Mon Sep 17 00:00:00 2001
From: Paolo Abeni <[email protected]>
Date: Thu, 8 Feb 2024 19:03:51 +0100
Subject: [PATCH] mptcp: fix more tx path fields initialization

The 'msk->write_seq' and 'msk->snd_nxt' are always updated under the msk socket lock, except at MPC handshake completiont time.

Builds-up on the previous commit to move such init under the relevant lock.

There are no known problems caused by the potential race, the primary goal is consistency.

index 7632eafb683b..8cb6a873dae9 100644
@@ -3478,10 +3478,8 @@ void mptcp_finish_connect(struct sock *ssk)
 	 * accessing the field below
 	 */
 	WRITE_ONCE(msk->local_key, subflow->local_key);
-	WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
-	WRITE_ONCE(msk->snd_nxt, msk->write_seq);
-	WRITE_ONCE(msk->snd_una, msk->write_seq);
-	WRITE_ONCE(msk->wnd_end, msk->snd_nxt + tcp_sk(ssk)->snd_wnd);
+	WRITE_ONCE(msk->snd_una, subflow->idsn + 1);
+	WRITE_ONCE(msk->wnd_end, subflow->idsn + 1 + tcp_sk(ssk)->snd_wnd);
 
 	mptcp_pm_new_connection(msk, ssk, 0);
 }

index 56b2ac2f2f22..c2df34ebcf28 100644
@@ -421,12 +421,21 @@ static bool subflow_use_different_dport(struct mptcp_sock *msk, const struct soc
 
 void __mptcp_sync_state(struct sock *sk, int state)
 {
+	struct mptcp_subflow_context *subflow;
 	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sock *ssk = msk->first;
 
-	__mptcp_propagate_sndbuf(sk, msk->first);
+	subflow = mptcp_subflow_ctx(ssk);
+	__mptcp_propagate_sndbuf(sk, ssk);
 	if (!msk->rcvspace_init)
-		mptcp_rcv_space_init(msk, msk->first);
+		mptcp_rcv_space_init(msk, ssk);
+
 	if (sk->sk_state == TCP_SYN_SENT) {
+		/* subflow->idsn is always available is TCP_SYN_SENT state,
+		 * even for the FASTOPEN scenarios
+		 */
+		WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
+		WRITE_ONCE(msk->snd_nxt, msk->write_seq);
 		mptcp_set_state(sk, state);
 		sk->sk_state_change(sk);
 	}