FAILED: patch "[PATCH] mptcp: fix more tx path fields initialization" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-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-6.1.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 '2024021911-fragment-yearly-5b45@gregkh' --subject-prefix 'PATCH 6.1.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")
a5efdbcece83 ("mptcp: fix delegated action races")
27e5ccc2d5a5 ("mptcp: fix dangling connection hang-up") f6909dc1c1f4 ("mptcp: rename timer related helper to less confusing names") 9f1a98813b4b ("mptcp: process pending subflow error on close") d5fbeff1ab81 ("mptcp: move __mptcp_error_report in protocol.c") ebc1e08f01eb ("mptcp: drop last_snd and MPTCP_RESET_SCHEDULER") e263691773cd ("mptcp: Remove unnecessary test for __mptcp_init_sock()") 39880bd808ad ("mptcp: get rid of msk->subflow")
3f326a821b99 ("mptcp: change the mpc check helper to return a sk") 3aa362494170 ("mptcp: avoid ssock usage in mptcp_pm_nl_create_listen_socket()") f0bc514bd5c1 ("mptcp: avoid additional indirection in sockopt") 40f56d0c7043 ("mptcp: avoid additional indirection in mptcp_listen()") 8cf2ebdc0078 ("mptcp: mptcp: avoid additional indirection in mptcp_bind()") ccae357c1c6a ("mptcp: avoid additional __inet_stream_connect() call")

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);
 	}

Hi Greg,

(...)

FYI, because of the various conflicts, and because "there are no known problems caused by the potential race", with Paolo, we think it is best not to backport this patch to v6.1 and older.

Cheers,
Matt

Sponsored by the NGI0 Core fund.

Thanks for the review of all of these and letting us know,

greg k-h