[PATCH 3.19 086/123] xen/events: avoid NULL pointer dereference in dom0 on large machines

From: Greg Kroah-Hartman
Date: Tue Mar 24 2015 - 13:14:03 EST


3.19-stable review patch. If anyone has any objections, please let me know.

------------------

From: Juergen Gross <jgross@xxxxxxxx>

commit 85e40b0539b24518c8bdf63e2605c8522377d00f upstream.

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@xxxxxxxx>
Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/xen/events/events_base.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -526,20 +526,26 @@ static unsigned int __startup_pirq(unsig
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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