CVE-2026-64206: Bluetooth: L2CAP: cancel pending_rx_work before taking conn->lock

From: Greg Kroah-Hartman <[email protected]>

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

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

Bluetooth: L2CAP: cancel pending_rx_work before taking conn->lock

l2cap_conn_del() takes conn->lock and then calls cancel_work_sync() for
pending_rx_work.  process_pending_rx() takes the same mutex, so teardown
can deadlock against the worker it is flushing.

This issue was found by our static analysis tool and then manually
reviewed against the current tree.

The grounded PoC kept the l2cap_conn_ready() -> queue_work(...,
&conn->pending_rx_work) submit path, the l2cap_conn_del() ->
cancel_work_sync(&conn->pending_rx_work) teardown path, and the
process_pending_rx() -> mutex_lock(&conn->lock) worker edge.  Lockdep

  WARNING: possible circular locking dependency detected
  process_pending_rx+0x21/0x2a [vuln_msv]
  l2cap_conn_del.constprop.0+0x3f/0x4e [vuln_msv]
  *** DEADLOCK ***

Cancel pending_rx_work before taking conn->lock, matching the existing
lock-before-drain ordering used for the two delayed works in the same
teardown path.  The pending_rx queue is still purged after the work has
been cancelled and conn->lock has been acquired.

The Linux kernel CVE team has assigned CVE-2026-64206 to this issue.


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

	Issue introduced in 3.16 with commit 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 and fixed in 6.18.39 with commit d5616beb3355b5fca2280d796c1cf7ada4ee6551
	Issue introduced in 3.16 with commit 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 and fixed in 7.1.4 with commit e96fbac8d3a73b0bc165383c092a30628561d320
	Issue introduced in 3.16 with commit 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 and fixed in 7.2-rc3 with commit 2641a9e0a1dd4af2e21995470a21d55dd35e5203
	Issue introduced in 3.15.5 with commit ee805f9499ebd0edf0877990968543c752043b59

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-2026-64206
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:
	net/bluetooth/l2cap_core.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/d5616beb3355b5fca2280d796c1cf7ada4ee6551
	https://git.kernel.org/stable/c/e96fbac8d3a73b0bc165383c092a30628561d320
	https://git.kernel.org/stable/c/2641a9e0a1dd4af2e21995470a21d55dd35e5203