drivers: staging: rtl8192u: Fix deadlock in ieee80211_beacons_stop()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drivers: staging: rtl8192u: Fix deadlock in ieee80211_beacons_stop() There is a deadlock in ieee80211_beacons_stop(), which is shown below: (Thread 1) | (Thread 2) | ieee80211_send_beacon() ieee80211_beacons_stop() | mod_timer() spin_lock_irqsave() //(1) | (wait a time) ... | ieee80211_send_beacon_cb() del_timer_sync() | spin_lock_irqsave() //(2) (wait timer to stop) | ... We hold ieee->beacon_lock in position (1) of thread 1 and use del_timer_sync() to wait timer to stop, but timer handler also need ieee->beacon_lock in position (2) of thread 2. As a result, ieee80211_beacons_stop() will block forever. This patch extracts del_timer_sync() from the protection of spin_lock_irqsave(), which could let timer handler to obtain the needed lock.

References

• https://git.kernel.org/stable/c/b465bb2ebf666116c1ac745cb80c65154dc0d27e
• https://git.kernel.org/stable/c/1fbe033c52480f7954c057510040fa6286c4ea25
• https://git.kernel.org/stable/c/66f769762f65d957f688f3258755c6ec410bf710
• https://git.kernel.org/stable/c/042915c1bfedd684c1d98a841794ee203200571a
• https://git.kernel.org/stable/c/ffc9cab7243f8151be37966301307bfd3cda2db3
• https://git.kernel.org/stable/c/b34cb54923a6e5ddefbaf358c85c922c6ab456e2
• https://git.kernel.org/stable/c/806c7b53414934ba2a39449b31fd1a038e500273