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 stable@vger.kernel.org.

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 14c56686a64c65ba716ff48f1f4b19c85f4cb2a9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023102022-wrongness-buddhism-fcf4@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 14c56686a64c65ba716ff48f1f4b19c85f4cb2a9 Mon Sep 17 00:00:00 2001 From: Geliang Tang geliang.tang@suse.com Date: Wed, 18 Oct 2023 11:23:55 -0700 Subject: [PATCH] mptcp: avoid sending RST when closing the initial subflow

When closing the first subflow, the MPTCP protocol unconditionally calls tcp_disconnect(), which in turn generates a reset if the subflow is established.

That is unexpected and different from what MPTCP does with MPJ subflows, where resets are generated only on FASTCLOSE and other edge scenarios.

We can't reuse for the first subflow the same code in place for MPJ subflows, as MPTCP clean them up completely via a tcp_close() call, while must keep the first subflow socket alive for later re-usage, due to implementation constraints.

This patch adds a new helper __mptcp_subflow_disconnect() that encapsulates, a logic similar to tcp_close, issuing a reset only when the MPTCP_CF_FASTCLOSE flag is set, and performing a clean shutdown otherwise.

Fixes: c2b2ae3925b6 ("mptcp: handle correctly disconnect() failures") Cc: stable@vger.kernel.org Reviewed-by: Matthieu Baerts matttbe@kernel.org Co-developed-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Geliang Tang geliang.tang@suse.com Signed-off-by: Mat Martineau martineau@kernel.org Link: https://lore.kernel.org/r/20231018-send-net-20231018-v1-4-17ecb002e41d@kerne... Signed-off-by: Jakub Kicinski kuba@kernel.org

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 4e30e5ba3795..886ab689a8ae 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2348,6 +2348,26 @@ bool __mptcp_retransmit_pending_data(struct sock *sk) #define MPTCP_CF_PUSH BIT(1) #define MPTCP_CF_FASTCLOSE BIT(2)

+/* be sure to send a reset only if the caller asked for it, also + * clean completely the subflow status when the subflow reaches + * TCP_CLOSE state + */ +static void __mptcp_subflow_disconnect(struct sock *ssk, + struct mptcp_subflow_context *subflow, + unsigned int flags) +{ + if (((1 << ssk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || + (flags & MPTCP_CF_FASTCLOSE)) { + /* The MPTCP code never wait on the subflow sockets, TCP-level + * disconnect should never fail + */ + WARN_ON_ONCE(tcp_disconnect(ssk, 0)); + mptcp_subflow_ctx_reset(subflow); + } else { + tcp_shutdown(ssk, SEND_SHUTDOWN); + } +} + /* subflow sockets can be either outgoing (connect) or incoming * (accept). * @@ -2385,7 +2405,7 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);

if ((flags & MPTCP_CF_FASTCLOSE) && !__mptcp_check_fallback(msk)) { - /* be sure to force the tcp_disconnect() path, + /* be sure to force the tcp_close path * to generate the egress reset */ ssk->sk_lingertime = 0; @@ -2395,11 +2415,7 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,

need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk); if (!dispose_it) { - /* The MPTCP code never wait on the subflow sockets, TCP-level - * disconnect should never fail - */ - WARN_ON_ONCE(tcp_disconnect(ssk, 0)); - mptcp_subflow_ctx_reset(subflow); + __mptcp_subflow_disconnect(ssk, subflow, flags); release_sock(ssk);

goto out;