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Subject: Re: [BUG] xen: Two possible sleep-in-atomic-context bugs in
 bind_evtchn_to_irqhandler()
To:     Jia-Ju Bai <baijiaju1990@gmail.com>,
        Stefano Stabellini <sstabellini@kernel.org>
Cc:     Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <80315b22-63c1-c8cc-1035-11fa36bee83a@gmail.com>
From:   Juergen Gross <jgross@suse.com>
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Date:   Wed, 20 Jun 2018 08:57:12 +0200
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On 20/06/18 04:49, Jia-Ju Bai wrote:
> 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.

Right, I think calling create_active() should be done before taking the
lock. Stefano, what do you think?


Juergen