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@invisiblethingslab.com Cc: stable@vger.kernel.org Reported-by: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com Signed-off-by: Juergen Gross jgross@suse.com --- 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;