There have been reports of races in evtchn_from_irq() where the info
pointer has been NULL.
Avoid that case by testing info before dereferencing it.
In order to avoid accessing a just freed info structure do the kfree()
via kfree_rcu().
Cc: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
drivers/xen/events/events_base.c | 10 ++++++++--
drivers/xen/events/events_internal.h | 3 +++
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 499eff7d3f65..838762fe3d6e 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -247,10 +247,16 @@ static void xen_irq_info_cleanup(struct irq_info *info)
*/
unsigned int evtchn_from_irq(unsigned irq)
{
+ struct irq_info *info;
+
if (WARN(irq >= nr_irqs, "Invalid irq %d!\n", irq))
return 0;
- return info_for_irq(irq)->evtchn;
+ info = info_for_irq(irq);
+ if (info == NULL)
+ return 0;
+
+ return info->evtchn;
}
unsigned irq_from_evtchn(unsigned int evtchn)
@@ -436,7 +442,7 @@ static void xen_free_irq(unsigned irq)
WARN_ON(info->refcnt > 0);
- kfree(info);
+ kfree_rcu(info, rcu);
/* Legacy IRQ descriptors are managed by the arch. */
if (irq < nr_legacy_irqs())
diff --git a/drivers/xen/events/events_internal.h b/drivers/xen/events/events_internal.h
index 82938cff6c7a..c421055843c8 100644
--- a/drivers/xen/events/events_internal.h
+++ b/drivers/xen/events/events_internal.h
@@ -7,6 +7,8 @@
#ifndef __EVENTS_INTERNAL_H__
#define __EVENTS_INTERNAL_H__
+#include <linux/rcupdate.h>
+
/* Interrupt types. */
enum xen_irq_type {
IRQT_UNBOUND = 0,
@@ -30,6 +32,7 @@ enum xen_irq_type {
*/
struct irq_info {
struct list_head list;
+ struct rcu_head rcu;
int refcnt;
enum xen_irq_type type; /* type */
unsigned irq;
--
2.16.4
