linux-kernel - Re: [PATCH] xen: avoid NULL pointer dereference in dom0 on large machines

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Date:	Fri, 06 Mar 2015 13:32:56 +0100
From:	Juergen Gross <jgross@...e.com>
To:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	konrad.wilk@...cle.com, david.vrabel@...rix.com,
	boris.ostrovsky@...cle.com
Subject: Re: [PATCH] xen: avoid NULL pointer dereference in dom0 on large
 machines

Ping?

On 02/26/2015 06:52 AM, Juergen Gross wrote:
> Using the pvops kernel a NULL pointer dereference was detected on a
> large machine (144 processors) when booting as dom0 in
> evtchn_fifo_unmask() during assignment of a pirq.
>
> The event channel in question was the first to need a new entry in
> event_array[] in events_fifo.c. Unfortunately xen_irq_info_pirq_setup()
> is called with evtchn being 0 for a new pirq and the real event channel
> number is assigned to the pirq only during __startup_pirq().
>
> It is mandatory to call xen_evtchn_port_setup() after assigning the
> event channel number to the pirq to make sure all memory needed for the
> event channel is allocated.
>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
>   drivers/xen/events/events_base.c | 18 ++++++++++++------
>   1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
> index b4bca2d..70fba97 100644
> --- a/drivers/xen/events/events_base.c
> +++ b/drivers/xen/events/events_base.c
> @@ -526,20 +526,26 @@ static unsigned int __startup_pirq(unsigned int irq)
>   	pirq_query_unmask(irq);
>
>   	rc = set_evtchn_to_irq(evtchn, irq);
> -	if (rc != 0) {
> -		pr_err("irq%d: Failed to set port to irq mapping (%d)\n",
> -		       irq, rc);
> -		xen_evtchn_close(evtchn);
> -		return 0;
> -	}
> +	if (rc)
> +		goto err;
> +
>   	bind_evtchn_to_cpu(evtchn, 0);
>   	info->evtchn = evtchn;
>
> +	rc = xen_evtchn_port_setup(info);
> +	if (rc)
> +		goto err;
> +
>   out:
>   	unmask_evtchn(evtchn);
>   	eoi_pirq(irq_get_irq_data(irq));
>
>   	return 0;
> +
> +err:
> +	pr_err("irq%d: Failed to set port to irq mapping (%d)\n", irq, rc);
> +	xen_evtchn_close(evtchn);
> +	return 0;
>   }
>
>   static unsigned int startup_pirq(struct irq_data *data)
>

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