[BUG] xen: Two possible sleep-in-atomic-context bugs in bind_evtchn_to_irqhandler()

[Jia-Ju Bai]

The driver may sleep with holding a spinlock.
The function call paths (from bottom to top) in Linux-4.16.7 are:

[FUNC] mutex_lock_nested --> can sleep
drivers/xen/events/events_base.c, 839: mutex_lock_nested in 
bind_evtchn_to_irq
drivers/xen/events/events_base.c, 1030: bind_evtchn_to_irq in 
bind_evtchn_to_irqhandler
drivers/xen/pvcalls-front.c, 371: bind_evtchn_to_irqhandler in create_active
drivers/xen/pvcalls-front.c, 417: create_active in pvcalls_front_connect
drivers/xen/pvcalls-front.c, 410: spin_lock in pvcalls_front_connect

[FUNC] request_irq --> can sleep
drivers/xen/events/events_base.c, 1003: request_irq in 
bind_evtchn_to_irqhandler
drivers/xen/pvcalls-front.c, 371: bind_evtchn_to_irqhandler in create_active
drivers/xen/pvcalls-front.c, 417: create_active in pvcalls_front_connect
drivers/xen/pvcalls-front.c, 410: spin_lock in pvcalls_front_connect

These bugs are found by my static analysis tool (DSAC-2) and checked by my
code review.

I do not know how to correctly fix these bugs, so I just report them.
Maybe create_active() should not be called with holding a spinlock.


Best wishes,
Jia-Ju Bai