Merge branch 'mptcp-pm-fix-ids-not-being-reusable'

Matthieu Baerts says:

====================
mptcp: pm: fix IDs not being reusable

Here are more fixes for the MPTCP in-kernel path-manager. In this
series, the fixes are around the endpoint IDs not being reusable for
on-going connections when re-creating endpoints with previously used IDs.

- Patch 1 fixes this case for endpoints being used to send ADD_ADDR.
  Patch 2 validates this fix. The issue is present since v5.10.

- Patch 3 fixes this case for endpoints being used to establish new
  subflows. Patch 4 validates this fix. The issue is present since v5.10.

- Patch 5 fixes this case when all endpoints are flushed. Patch 6
  validates this fix. The issue is present since v5.13.

- Patch 7 removes a helper that is confusing, and introduced in v5.10.
  It helps simplifying the next patches.

- Patch 8 makes sure a 'subflow' counter is only decremented when
  removing a 'subflow' endpoint. Can be backported up to v5.13.

- Patch 9 is similar, but for a 'signal' counter. Can be backported up
  to v5.10.

- Patch 10 checks the last max accepted ADD_ADDR limit before accepting
  new ADD_ADDR. For v5.10 as well.

- Patch 11 removes a wrong restriction for the userspace PM, added
  during a refactoring in v6.5.

- Patch 12 makes sure the fullmesh mode sets the ID 0 when a new subflow
  using the source address of the initial subflow is created. Patch 13
  covers this case. This issue is present since v5.15.

- Patch 14 avoid possible UaF when selecting an address from the
  endpoints list.
====================

Link: https://patch.msgid.link/20240819-net-mptcp-pm-reusing-id-v1-0-38035d40de5b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>