CVE-2026-64043: ovpn: fix race between deleting interface and adding new peer

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

ovpn: fix race between deleting interface and adding new peer

While deleting an existing ovpn interface, there is a very
narrow window where adding a new peer via netlink may cause
the netdevice to hang and prevent its unregistration.

It may happen during ovpn_dellink(), when all existing peers are
freed and the device is queued for deregistration, but a
CMD_PEER_NEW message comes in adding a new peer that takes again
a reference to the netdev.

At this point there is no way to release the device because we are
under the assumption that all peers were already released.

Fix the race condition by releasing all peers in ndo_uninit(),
when the netdevice has already been removed from the netdev
list.

Also ovpn_peer_add() has now an extra check that forces the
function to bail out if the device reg_state is not REGISTERED.
This way any incoming CMD_PEER_NEW racing with the interface
deletion routine will simply stop before adding the peer.

Note that the above check happens while holding the netdev_lock
to prevent racing netdev state changes.

ovpn_dellink() is now empty and can be removed.

The Linux kernel CVE team has assigned CVE-2026-64043 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.16 with commit 80747caef33d77f5c1b3d24644e6d7dae69066b5 and fixed in 6.18.34 with commit 097d62df38314c14b88fab9096f3461baf158e2b
	Issue introduced in 6.16 with commit 80747caef33d77f5c1b3d24644e6d7dae69066b5 and fixed in 7.0.11 with commit de9fec2a6645f5b4d23398cd870a33e2703728d9
	Issue introduced in 6.16 with commit 80747caef33d77f5c1b3d24644e6d7dae69066b5 and fixed in 7.1 with commit 982422b11e6f95f766a8cd2c2b1cbdb77e234a61

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-64043
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/net/ovpn/main.c
	drivers/net/ovpn/peer.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/097d62df38314c14b88fab9096f3461baf158e2b
	https://git.kernel.org/stable/c/de9fec2a6645f5b4d23398cd870a33e2703728d9
	https://git.kernel.org/stable/c/982422b11e6f95f766a8cd2c2b1cbdb77e234a61