FAILED: patch "[PATCH] mptcp: pm: re-using ID of unused removed ADD_ADDR" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] mptcp: pm: re-using ID of unused removed ADD_ADDR" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x e255683c06df572ead96db5efb5d21be30c0efaa
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024082621-unluckily-aghast-028b@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

e255683c06df ("mptcp: pm: re-using ID of unused removed ADD_ADDR")
4b317e0eb287 ("mptcp: fix NL PM announced address accounting")
6fa0174a7c86 ("mptcp: more careful RM_ADDR generation")
7d9bf018f907 ("selftests: mptcp: update output info of chk_rm_nr")
327b9a94e2a8 ("selftests: mptcp: more stable join tests-cases")

thanks,

greg k-h

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

From e255683c06df572ead96db5efb5d21be30c0efaa Mon Sep 17 00:00:00 2001
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Mon, 19 Aug 2024 21:45:19 +0200
Subject: [PATCH] mptcp: pm: re-using ID of unused removed ADD_ADDR

If no subflow is attached to the 'signal' endpoint that is being
removed, the addr ID will not be marked as available again.

Mark the linked ID as available when removing the address entry from the
list to cover this case.

Fixes: b6c08380860b ("mptcp: remove addr and subflow in PM netlink")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20240819-net-mptcp-pm-reusing-id-v1-1-38035d40de5b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 4cae2aa7be5c..26f0329e16bb 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -1431,7 +1431,10 @@ static bool mptcp_pm_remove_anno_addr(struct mptcp_sock *msk,
 	ret = remove_anno_list_by_saddr(msk, addr);
 	if (ret || force) {
 		spin_lock_bh(&msk->pm.lock);
-		msk->pm.add_addr_signaled -= ret;
+		if (ret) {
+			__set_bit(addr->id, msk->pm.id_avail_bitmap);
+			msk->pm.add_addr_signaled--;
+		}
 		mptcp_pm_remove_addr(msk, &list);
 		spin_unlock_bh(&msk->pm.lock);
 	}

Re: FAILED: patch "[PATCH] mptcp: pm: re-using ID of unused removed ADD_ADDR" failed to apply to 5.15-stable tree

[Matthieu Baerts]

Hi Greg,

On 26/08/2024 15:37, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 5.15-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>.

Thank you for the notification!

(...)

> ------------------ original commit in Linus's tree ------------------
> 
> From e255683c06df572ead96db5efb5d21be30c0efaa Mon Sep 17 00:00:00 2001
> From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
> Date: Mon, 19 Aug 2024 21:45:19 +0200
> Subject: [PATCH] mptcp: pm: re-using ID of unused removed ADD_ADDR
> 
> If no subflow is attached to the 'signal' endpoint that is being
> removed, the addr ID will not be marked as available again.
> 
> Mark the linked ID as available when removing the address entry from the
> list to cover this case.
> 
> Fixes: b6c08380860b ("mptcp: remove addr and subflow in PM netlink")

FYI, I think it is best not to backport this patch to v5.15: to fix the
issue, we need commit 86e39e04482b ("mptcp: keep track of local endpoint
still available for each msk") as well. This other commit is modifying
quite a bit of code, it depends on other ones, and it was seen as a new
feature at that time. Even if it improves the user experience, I think
it is best to consider this as an improvement, and keep the "annoying
behaviours", including the one being fixed here, as "known issues" in
this version.

In other words, I don't think we need to backport this patch to v5.15.

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