xen: don't leak IRQs over suspend/resume.

On resume irq_info[*].evtchn is reset to 0 since event channel mappings
are not preserved over suspend/resume. The other contents of irq_info
is preserved to allow rebind_evtchn_irq() to function.

However when a device resumes it will try to unbind from the
previous IRQ (e.g.  blkfront goes blkfront_resume() -> blkif_free() ->
unbind_from_irqhandler() -> unbind_from_irq()). This will fail due to the
check for VALID_EVTCHN in unbind_from_irq() and the IRQ is leaked. The
device will then continue to resume and allocate a new IRQ, eventually
leading to find_unbound_irq() panic()ing.

Fix this by changing unbind_from_irq() to handle teardown of interrupts
which have type!=IRQT_UNBOUND but are not currently bound to a specific
event channel.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stable Kernel <stable@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 2f57276e87a2..ce602dd09bc1 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -474,6 +474,9 @@ static void unbind_from_irq(unsigned int irq)
                 bind_evtchn_to_cpu(evtchn, 0);
 
                 evtchn_to_irq[evtchn] = -1;
+        }
+
+        if (irq_info[irq].type != IRQT_UNBOUND) {
                 irq_info[irq] = mk_unbound_info();
 
                 dynamic_irq_cleanup(irq);