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

wifi: ath9k: hif_usb: don't dereference hif_dev after re-arming firmware request

ath9k_hif_request_firmware() re-arms an asynchronous firmware load via
request_firmware_nowait(), passing hif_dev as the completion context, and
then still dereferences hif_dev:

	dev_info(&hif_dev->udev->dev, "ath9k_htc: Firmware %s requested\n",
		 hif_dev->fw_name);

The re-armed callback ath9k_hif_usb_firmware_cb() runs on the "events"
workqueue and, when the firmware is missing, walks the retry chain into
ath9k_hif_usb_firmware_fail() -> complete_all(&hif_dev->fw_done). That
releases the wait_for_completion(&hif_dev->fw_done) in a concurrent
ath9k_hif_usb_disconnect(), which then kfree()s hif_dev. The trailing
dev_info() in the frame that re-armed the request can therefore read freed
memory (hif_dev->udev, the first field of struct hif_device_usb):

  BUG: KASAN: slab-use-after-free in ath9k_hif_request_firmware
  Read of size 8 ... by task kworker/...
   ath9k_hif_request_firmware
   ath9k_hif_usb_firmware_cb           drivers/net/wireless/ath/ath9k/hif_usb.c:1247
   request_firmware_work_func
  Allocated by ...:
   ath9k_hif_usb_probe                 drivers/net/wireless/ath/ath9k/hif_usb.c
  Freed by ...:
   ath9k_hif_usb_disconnect -> kfree   drivers/net/wireless/ath/ath9k/hif_usb.c

The fw_done barrier only makes disconnect wait for the firmware chain to
*terminate*; it does not protect the outer ath9k_hif_request_firmware()
frame that re-armed the request and keeps touching hif_dev afterwards.

Drop the post-request dev_info(): it is the only use of hif_dev after the
async request is armed, and it is purely informational (the dev_err() on the
failure path runs only when request_firmware_nowait() did not arm a callback,
so hif_dev is still alive there).

This was first reported by syzbot as a single, non-reproduced crash that was
later auto-obsoleted, and was independently rediscovered by the reFuzz fuzzer,
which produced a C reproducer (USB-gadget connect/disconnect of an ath9k_htc
device whose firmware download fails). The vulnerable code is unchanged and
still present in v7.1-rc6, where the slab-use-after-free reproduces under KASAN
once the (sub-microsecond) race window is widened.

https://git.kernel.org/stable/c/10b0ce629123a3737b4eda50188f73bb7be7b68b

https://git.kernel.org/stable/c/48a69cedde7388294e4ea6fd804156cd62bc04fc

https://git.kernel.org/stable/c/7c9046d92c4b9789c9d9d775e4fd5f34be64cb0a

https://git.kernel.org/stable/c/7f184ca38a90889f3f6665ff96748b95da39dbee

https://git.kernel.org/stable/c/dad9f96945d77ecd4708f730c06ef54dcd8cc057

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