From: Juergen Gross <jgross@suse.com>
Date: Mon, 15 Mar 2021 09:22:37 +0100
Subject: xen/events: reset affinity of 2-level event when tearing it down
Patch-mainline: v5.12-rc3
Git-commit: 9e77d96b8e2724ed00380189f7b0ded61113b39f
References: bsc#1183638 XSA-332 CVE-2020-27673

When creating a new event channel with 2-level events the affinity
needs to be reset initially in order to avoid using an old affinity
from earlier usage of the event channel port. So when tearing an event
channel down reset all affinity bits.

The same applies to the affinity when onlining a vcpu: all old
affinity settings for this vcpu must be reset. As percpu events get
initialized before the percpu event channel hook is called,
resetting of the affinities happens after offlining a vcpu (this is
working, as initial percpu memory is zeroed out).

Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Link: https://lore.kernel.org/r/20210306161833.4552-2-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
 drivers/xen/events/events_2l.c       | 15 +++++++++++++++
 drivers/xen/events/events_base.c     |  1 +
 drivers/xen/events/events_internal.h |  8 ++++++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/xen/events/events_2l.c b/drivers/xen/events/events_2l.c
index f026624898e7..cf3f579c1c3d 100644
--- a/drivers/xen/events/events_2l.c
+++ b/drivers/xen/events/events_2l.c
@@ -47,6 +47,11 @@ static unsigned evtchn_2l_max_channels(void)
 	return EVTCHN_2L_NR_CHANNELS;
 }
 
+static void evtchn_2l_remove(evtchn_port_t evtchn, unsigned int cpu)
+{
+	clear_bit(evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
+}
+
 static void evtchn_2l_bind_to_cpu(struct irq_info *info, unsigned cpu)
 {
 	clear_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, info->cpu)));
@@ -354,9 +359,18 @@ static void evtchn_2l_resume(void)
 				EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
 }
 
+static int evtchn_2l_percpu_deinit(unsigned int cpu)
+{
+	memset(per_cpu(cpu_evtchn_mask, cpu), 0, sizeof(xen_ulong_t) *
+			EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
+
+	return 0;
+}
+
 static const struct evtchn_ops evtchn_ops_2l = {
 	.max_channels      = evtchn_2l_max_channels,
 	.nr_channels       = evtchn_2l_max_channels,
+	.remove            = evtchn_2l_remove,
 	.bind_to_cpu       = evtchn_2l_bind_to_cpu,
 	.clear_pending     = evtchn_2l_clear_pending,
 	.set_pending       = evtchn_2l_set_pending,
@@ -366,6 +380,7 @@ static const struct evtchn_ops evtchn_ops_2l = {
 	.unmask            = evtchn_2l_unmask,
 	.handle_events     = evtchn_2l_handle_events,
 	.resume	           = evtchn_2l_resume,
+	.percpu_deinit     = evtchn_2l_percpu_deinit,
 };
 
 void __init xen_evtchn_2l_init(void)
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 7b94a6c31664..2e4c4ab38095 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -286,6 +286,7 @@ static int xen_irq_info_pirq_setup(unsigned irq,
 static void xen_irq_info_cleanup(struct irq_info *info)
 {
 	set_evtchn_to_irq(info->evtchn, -1);
+	xen_evtchn_port_remove(info->evtchn, info->cpu);
 	info->evtchn = 0;
 }
 
diff --git a/drivers/xen/events/events_internal.h b/drivers/xen/events/events_internal.h
index a35c8c7ac606..6ccebc498679 100644
--- a/drivers/xen/events/events_internal.h
+++ b/drivers/xen/events/events_internal.h
@@ -65,6 +65,7 @@ struct evtchn_ops {
 	unsigned (*nr_channels)(void);
 
 	int (*setup)(struct irq_info *info);
+	void (*remove)(evtchn_port_t port, unsigned int cpu);
 	void (*bind_to_cpu)(struct irq_info *info, unsigned cpu);
 
 	void (*clear_pending)(unsigned port);
@@ -107,6 +108,13 @@ static inline int xen_evtchn_port_setup(struct irq_info *info)
 	return 0;
 }
 
+static inline void xen_evtchn_port_remove(evtchn_port_t evtchn,
+					  unsigned int cpu)
+{
+	if (evtchn_ops->remove)
+		evtchn_ops->remove(evtchn, cpu);
+}
+
 static inline void xen_evtchn_port_bind_to_cpu(struct irq_info *info,
 					       unsigned cpu)
 {
-- 
2.26.2