wifi: ath9k: Fix use-after-free in ath9k_hif_usb_disconnect()

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

wifi: ath9k: Fix use-after-free in ath9k_hif_usb_disconnect()

This patch fixes a use-after-free in ath9k that occurs in
ath9k_hif_usb_disconnect() when ath9k_destroy_wmi() is trying to access
'drv_priv' that has already been freed by ieee80211_free_hw(), called by
ath9k_htc_hw_deinit(). The patch moves ath9k_destroy_wmi() before
ieee80211_free_hw(). Note that urbs from the driver should be killed
before freeing 'wmi' with ath9k_destroy_wmi() as their callbacks will
access 'wmi'.

Found by a modified version of syzkaller.

==================================================================
BUG: KASAN: use-after-free in ath9k_destroy_wmi+0x38/0x40
Read of size 8 at addr ffff8881069132a0 by task kworker/0:1/7

CPU: 0 PID: 7 Comm: kworker/0:1 Tainted: G O 5.14.0+ #131
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
Workqueue: usb_hub_wq hub_event
Call Trace:
dump_stack_lvl+0x8e/0xd1
print_address_description.constprop.0.cold+0x93/0x334
? ath9k_destroy_wmi+0x38/0x40
? ath9k_destroy_wmi+0x38/0x40
kasan_report.cold+0x83/0xdf
? ath9k_destroy_wmi+0x38/0x40
ath9k_destroy_wmi+0x38/0x40
ath9k_hif_usb_disconnect+0x329/0x3f0
? ath9k_hif_usb_suspend+0x120/0x120
? usb_disable_interface+0xfc/0x180
usb_unbind_interface+0x19b/0x7e0
? usb_autoresume_device+0x50/0x50
device_release_driver_internal+0x44d/0x520
bus_remove_device+0x2e5/0x5a0
device_del+0x5b2/0xe30
? __device_link_del+0x370/0x370
? usb_remove_ep_devs+0x43/0x80
? remove_intf_ep_devs+0x112/0x1a0
usb_disable_device+0x1e3/0x5a0
usb_disconnect+0x267/0x870
hub_event+0x168d/0x3950
? rcu_read_lock_sched_held+0xa1/0xd0
? hub_port_debounce+0x2e0/0x2e0
? check_irq_usage+0x860/0xf20
? drain_workqueue+0x281/0x360
? lock_release+0x640/0x640
? rcu_read_lock_sched_held+0xa1/0xd0
? rcu_read_lock_bh_held+0xb0/0xb0
? lockdep_hardirqs_on_prepare+0x273/0x3e0
process_one_work+0x92b/0x1460
? pwq_dec_nr_in_flight+0x330/0x330
? rwlock_bug.part.0+0x90/0x90
worker_thread+0x95/0xe00
? __kthread_parkme+0x115/0x1e0
? process_one_work+0x1460/0x1460
kthread+0x3a1/0x480
? set_kthread_struct+0x120/0x120
ret_from_fork+0x1f/0x30

The buggy address belongs to the page:
page:ffffea00041a44c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x106913
flags: 0x200000000000000(node=0|zone=2)
raw: 0200000000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), pid 7, ts 38347963444, free_ts 41399957635
prep_new_page+0x1aa/0x240
get_page_from_freelist+0x159a/0x27c0
__alloc_pages+0x2da/0x6a0
alloc_pages+0xec/0x1e0
kmalloc_order+0x39/0xf0
kmalloc_order_trace+0x19/0x120
__kmalloc+0x308/0x390
wiphy_new_nm+0x6f5/0x1dd0
ieee80211_alloc_hw_nm+0x36d/0x2230
ath9k_htc_probe_device+0x9d/0x1e10
ath9k_htc_hw_init+0x34/0x50
ath9k_hif_usb_firmware_cb+0x25f/0x4e0
request_firmware_work_func+0x131/0x240
process_one_work+0x92b/0x1460
worker_thread+0x95/0xe00
kthread+0x3a1/0x480
page last free stack trace:
free_pcp_prepare+0x3d3/0x7f0
free_unref_page+0x1e/0x3d0
device_release+0xa4/0x240
kobject_put+0x186/0x4c0
put_device+0x20/0x30
ath9k_htc_disconnect_device+0x1cf/0x2c0
ath9k_htc_hw_deinit+0x26/0x30
ath9k_hif_usb_disconnect+0x2d9/0x3f0
usb_unbind_interface+0x19b/0x7e0
device_release_driver_internal+0x44d/0x520
bus_remove_device+0x2e5/0x5a0
device_del+0x5b2/0xe30
usb_disable_device+0x1e3/0x5a0
usb_disconnect+0x267/0x870
hub_event+0x168d/0x3950
process_one_work+0x92b/0x1460

Memory state around the buggy address:
ffff888106913180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff888106913200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888
---truncated---