5.5 - CVE-2022-49311

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

drivers: staging: rtl8192bs: Fix deadlock in rtw_joinbss_event_prehandle()

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

(Thread 1) | (Thread 2)
| _set_timer() rtw_joinbss_event_prehandle()| mod_timer()
spin_lock_bh() //(1) | (wait a time)
... | _rtw_join_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_joinbss_event_prehandle() 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() to spin_lock_irq() in _rtw_join_timeout_handler() in order to prevent deadlock.