CVE-2026-74575: thunderbolt: Prevent XDomain delayed work use-after-free on disconnect

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

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

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

thunderbolt: Prevent XDomain delayed work use-after-free on disconnect

tb_xdp_handle_request() runs on system_wq and queues
xd->state_work via queue_delayed_work() in three request handlers:
PROPERTIES_CHANGED_REQUEST, UUID_REQUEST (via start_handshake),
and LINK_STATE_CHANGE_REQUEST.  Similarly, update_xdomain() queues
xd->properties_changed_work when local properties change.

Concurrently, tb_xdomain_remove() calls stop_handshake() which does
cancel_delayed_work_sync() on both delayed works.  Later,
tb_xdomain_unregister() calls device_unregister() which eventually
frees the xdomain.  Since commit 559c1e1e0134 ("thunderbolt: Run
tb_xdp_handle_request() in system workqueue") moved the request
handler off tb->wq, the handler and the remove path are no longer
serialized.  If queue_delayed_work() executes after
cancel_delayed_work_sync() but before the xdomain is freed, the
delayed work fires on a freed object.

Add xd->removing that tb_xdomain_remove() sets under xd->lock
before calling stop_handshake().  Each external queue site holds
the same lock and checks removing before calling
queue_delayed_work().  This provides the mutual exclusion needed:
either the queue site acquires the lock first and queues work that
the subsequent cancel will see, or the remove path acquires the
lock first and the queue site observes removing == true and skips
the queue.

The Linux kernel CVE team has assigned CVE-2026-74575 to this issue.


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

	Issue introduced in 5.2 with commit 559c1e1e013437bf190469efbcbd8bc803285853 and fixed in 6.6.151 with commit 91b40862a02000f490b63f1d315be3ee31e83871
	Issue introduced in 5.2 with commit 559c1e1e013437bf190469efbcbd8bc803285853 and fixed in 6.12.103 with commit 33c0ee18cf8665c974b00f4e0ba769fbc07efe10
	Issue introduced in 5.2 with commit 559c1e1e013437bf190469efbcbd8bc803285853 and fixed in 6.18.44 with commit 54a62153c765cd24239cde1f2633f2a2fd005368
	Issue introduced in 5.2 with commit 559c1e1e013437bf190469efbcbd8bc803285853 and fixed in 7.1.8 with commit 2aa2cde2cc79a79d8ea4a15be9f4a67fc528ae91
	Issue introduced in 5.2 with commit 559c1e1e013437bf190469efbcbd8bc803285853 and fixed in 7.2-rc1 with commit 2c5d2d3c3f70cde2565d7b279b544893a2035842

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-2026-74575
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/thunderbolt/xdomain.c
	include/linux/thunderbolt.h


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/91b40862a02000f490b63f1d315be3ee31e83871
	https://git.kernel.org/stable/c/33c0ee18cf8665c974b00f4e0ba769fbc07efe10
	https://git.kernel.org/stable/c/54a62153c765cd24239cde1f2633f2a2fd005368
	https://git.kernel.org/stable/c/2aa2cde2cc79a79d8ea4a15be9f4a67fc528ae91
	https://git.kernel.org/stable/c/2c5d2d3c3f70cde2565d7b279b544893a2035842