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

drivers: staging: rtl8723bs: Fix deadlock in rtw_surveydone_event_callback()

There is a deadlock in rtw_surveydone_event_callback(),
which is shown below:

   (Thread 1)                  |      (Thread 2)
                               | _set_timer()
rtw_surveydone_event_callback()|  mod_timer()
 spin_lock_bh() //(1)          |  (wait a time)
 ...                           | rtw_scan_timeout_handler()
 del_timer_sync()              |  spin_lock_bh() //(2)
 (wait timer to stop)          |  ...

We hold pmlmepriv->lock in position (1) of thread 1 and use
del_timer_sync() to wait timer to stop, but timer handler
also need pmlmepriv->lock in position (2) of thread 2.
As a result, rtw_surveydone_event_callback() will block forever.

This patch extracts del_timer_sync() from the protection of
spin_lock_bh(), which could let timer handler to obtain
the needed lock. What`s more, we change spin_lock_bh() in
rtw_scan_timeout_handler() to spin_lock_irq(). Otherwise,
spin_lock_bh() will also cause deadlock() in timer handler.

https://git.kernel.org/stable/c/2c41f5c341853f84b7bc2f32605d4e2782e8c279

https://git.kernel.org/stable/c/cc7ad0d77b51c872d629bcd98aea463a3c4109e7

https://git.kernel.org/stable/c/ce129d3efd181da5fd56f4360cc8827122afa67e

https://git.kernel.org/stable/c/f89f6c3ebf69623b8ea48200bd690e9e210335a1