Hi Greg,

On 26/02/2024 14:17, gregkh@linuxfoundation.org wrote:

The patch below does not apply to the 5.15-stable tree.

(...)

Possible dependencies:

a7cfe7766370 ("mptcp: fix data races on local_id")
84c531f54ad9 ("mptcp: userspace pm send RM_ADDR for ID 0")
f1f26512a9bf ("mptcp: use plain bool instead of custom binary enum")
1e07938e29c5 ("net: mptcp: rename netlink handlers to mptcp_pm_nl_<blah>_{doit,dumpit}")
1d0507f46843 ("net: mptcp: convert netlink from small_ops to ops")
fce68b03086f ("mptcp: add scheduled in mptcp_subflow_context")
1730b2b2c5a5 ("mptcp: add sched in mptcp_sock")
740ebe35bd3f ("mptcp: add struct mptcp_sched_ops")
a7384f391875 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net")

(...)

From a7cfe776637004a4c938fde78be4bd608c32c3ef Mon Sep 17 00:00:00 2001
From: Paolo Abeni <pabeni@redhat.com>
Date: Thu, 15 Feb 2024 19:25:31 +0100
Subject: [PATCH] mptcp: fix data races on local_id

The local address id is accessed lockless by the NL PM, add
all the required ONCE annotation. There is a caveat: the local
id can be initialized late in the subflow life-cycle, and its
validity is controlled by the local_id_valid flag.

Remove such flag and encode the validity in the local_id field
itself with negative value before initialization. That allows
accessing the field consistently with a single read operation.

FYI, because of the various conflicts, and because the issue seems
unlikely is quite harmless -- e.g. a duplicated subflow is created --, I
think it is better not to try to backport this patch to v5.15 and older.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.