wifi: brcmsmac: fix UAF in brcms_free_timer()

In the Linux kernel, the following vulnerability has been resolved: wifi: brcmsmac: fix UAF in brcms_free_timer() brcms_free_timer() calls brcms_del_timer() which uses the non-synchronous cancel_delayed_work() to cancel the timer's underlying delayed work. If the work callback (_brcms_timer) is already running, cancel_delayed_work() returns false without waiting, and brcms_free_timer() proceeds to kfree(t) while the callback still accesses t through container_of(). Add an explicit cancel_delayed_work_sync() after brcms_del_timer() to guarantee that any in-flight callback has completed before the timer structure is freed.

Where it's fixed