CVE-2026-80947: wifi: rtl8xxxu: fix use-after-free from rx_urb_wq on stop

CVE-2026-80947: wifi: rtl8xxxu: fix use-after-free from rx_urb_wq on stop

[Greg Kroah-Hartman]

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

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

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

wifi: rtl8xxxu: fix use-after-free from rx_urb_wq on stop

rtl8xxxu arms rx_urb_wq from the RX completion path:
rtl8xxxu_rx_complete() hands the URB to rtl8xxxu_queue_rx_urb(), which
queues it on rx_urb_pending_list and, once the list grows past
RTL8XXXU_RX_URB_PENDING_WATER, schedules rx_urb_wq.  The worker
rtl8xxxu_rx_urb_work() drains rx_urb_pending_list, recovers priv through
container_of, and resubmits each URB through rtl8xxxu_submit_rx_urb(),
which anchors it on rx_anchor and dereferences priv->udev.

rtl8xxxu_stop() cancels the sibling work items (c2hcmd_work, ra_watchdog,
update_beacon_work) but never cancels rx_urb_wq, so a worker armed during
the last burst of RX traffic can run rtl8xxxu_rx_urb_work() after
rtl8xxxu_disconnect() has called ieee80211_free_hw(), which frees priv,
producing a use-after-free.  The window opens under active RX traffic
(pending count above the watermark) followed by a disconnect.

There are two teardown races to close:

  * rtl8xxxu_queue_rx_urb() decided whether to enqueue under rx_urb_lock
    but called schedule_work() after dropping the lock.  A completion
    that observed shutdown == false and released the lock could then call
    schedule_work() after rtl8xxxu_stop() had set shutdown and
    cancel_work_sync() had already returned, arming the worker to run
    after the teardown.  Move schedule_work() under the same !shutdown
    branch so the arming decision is atomic with the shutdown check.

  * rtl8xxxu_rx_urb_work() anchors every URB it drained back onto
    rx_anchor through rtl8xxxu_submit_rx_urb().  A worker still running
    when usb_kill_anchored_urbs(&priv->rx_anchor) returned would submit a
    URB that escaped the kill.  In rtl8xxxu_stop(), call
    cancel_work_sync(&priv->rx_urb_wq) before the kill so the worker is
    drained first.

After priv->shutdown is set under rx_urb_lock, completions can no longer
queue rx_urb_wq. cancel_work_sync() then drains the last queued or running
worker, and the following usb_kill_anchored_urbs() kills the URBs it may
have submitted.

rtl8xxxu_disconnect() is covered because ieee80211_unregister_hw()
guarantees .stop() runs for a live interface before ieee80211_free_hw()
frees priv.  The probe error path needs no cancel: rx_urb_wq is
INIT_WORK()'d there but cannot have been scheduled, since no URB is
submitted before ieee80211_register_hw() succeeds.

This bug was found by static analysis.

The Linux kernel CVE team has assigned CVE-2026-80947 to this issue.


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

	Issue introduced in 4.4 with commit 26f1fad29ad973b0fb26a9ca3dcb2a73dde781aa and fixed in 6.12.109 with commit 800d2b490a9af1e7132a3564c2ad5a81292e5b40
	Issue introduced in 4.4 with commit 26f1fad29ad973b0fb26a9ca3dcb2a73dde781aa and fixed in 6.18.50 with commit 620acb1e8037b73a457dc8ef20fc23fc7adcb405
	Issue introduced in 4.4 with commit 26f1fad29ad973b0fb26a9ca3dcb2a73dde781aa and fixed in 7.2.4 with commit 972ab8b9c08f3eb3fa535082de2950dd93604dfd
	Issue introduced in 4.4 with commit 26f1fad29ad973b0fb26a9ca3dcb2a73dde781aa and fixed in 7.3-rc1 with commit 6c080026ecc17eecb103f8927c64ea73a74bb818

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-2026-80947
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/wireless/realtek/rtl8xxxu/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/800d2b490a9af1e7132a3564c2ad5a81292e5b40
	https://git.kernel.org/stable/c/620acb1e8037b73a457dc8ef20fc23fc7adcb405
	https://git.kernel.org/stable/c/972ab8b9c08f3eb3fa535082de2950dd93604dfd
	https://git.kernel.org/stable/c/6c080026ecc17eecb103f8927c64ea73a74bb818