wifi: ath10k: avoid NULL pointer error during sdio remove
In the Linux kernel, the following vulnerability has been resolved:
wifi: ath10k: avoid NULL pointer error during sdio remove
When running 'rmmod ath10k', ath10k_sdio_remove() will free sdio
workqueue by destroy_workqueue(). But if CONFIG_INIT_ON_FREE_DEFAULT_ON
is set to yes, kernel panic will happen:
Call trace:
destroy_workqueue+0x1c/0x258
ath10k_sdio_remove+0x84/0x94
sdio_bus_remove+0x50/0x16c
device_release_driver_internal+0x188/0x25c
device_driver_detach+0x20/0x2c
This is because during 'rmmod ath10k', ath10k_sdio_remove() will call
ath10k_core_destroy() before destroy_workqueue(). wiphy_dev_release()
will finally be called in ath10k_core_destroy(). This function will free
struct cfg80211_registered_device *rdev and all its members, including
wiphy, dev and the pointer of sdio workqueue. Then the pointer of sdio
workqueue will be set to NULL due to CONFIG_INIT_ON_FREE_DEFAULT_ON.
After device release, destroy_workqueue() will use NULL pointer then the
kernel panic happen.
Call trace:
ath10k_sdio_remove
->ath10k_core_unregister
……
->ath10k_core_stop
->ath10k_hif_stop
->ath10k_sdio_irq_disable
->ath10k_hif_power_down
->del_timer_sync(&ar_sdio->sleep_timer)
->ath10k_core_destroy
->ath10k_mac_destroy
->ieee80211_free_hw
->wiphy_free
……
->wiphy_dev_release
->destroy_workqueue
Need to call destroy_workqueue() before ath10k_core_destroy(), free
the work queue buffer first and then free pointer of work queue by
ath10k_core_destroy(). This order matches the error path order in
ath10k_sdio_probe().
No work will be queued on sdio workqueue between it is destroyed and
ath10k_core_destroy() is called. Based on the call_stack above, the
reason is:
Only ath10k_sdio_sleep_timer_handler(), ath10k_sdio_hif_tx_sg() and
ath10k_sdio_irq_disable() will queue work on sdio workqueue.
Sleep timer will be deleted before ath10k_core_destroy() in
ath10k_hif_power_down().
ath10k_sdio_irq_disable() only be called in ath10k_hif_stop().
ath10k_core_unregister() will call ath10k_hif_power_down() to stop hif
bus, so ath10k_sdio_hif_tx_sg() won't be called anymore.
Tested-on: QCA6174 hw3.2 SDIO WLAN.RMH.4.4.1-00189
