refcount_t type and corresponding API can protect refcounters from
accidental underflow and overflow and further use-after-free situations.
Signed-off-by: Xiyu Yang <xiyuyang19@xxxxxxxxxxxx>
Signed-off-by: Xin Tan <tanxin.ctf@xxxxxxxxx>
---
drivers/block/xen-blkback/common.h | 7 ++++---
drivers/block/xen-blkback/xenbus.c | 2 +-
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index bda5c815e441..d074cf41b4bc 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -27,6 +27,7 @@
#ifndef __XEN_BLKIF__BACKEND__COMMON_H__
#define __XEN_BLKIF__BACKEND__COMMON_H__
+#include <linux/refcount.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
@@ -306,7 +307,7 @@ struct xen_blkif {
struct xen_vbd vbd;
/* Back pointer to the backend_info. */
struct backend_info *be;
- atomic_t refcnt;
+ refcount_t refcnt;
/* for barrier (drain) requests */
struct completion drain_complete;
atomic_t drain;
@@ -359,10 +360,10 @@ struct pending_req {
#define vbd_sz(_v) bdev_nr_sectors((_v)->bdev)
-#define xen_blkif_get(_b) (atomic_inc(&(_b)->refcnt))
+#define xen_blkif_get(_b) (refcount_inc(&(_b)->refcnt))
#define xen_blkif_put(_b) \
do { \
- if (atomic_dec_and_test(&(_b)->refcnt)) \
+ if (refcount_dec_and_test(&(_b)->refcnt)) \
schedule_work(&(_b)->free_work);\
} while (0)
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 125b22205d38..b0bd5faa3865 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -168,7 +168,7 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
return ERR_PTR(-ENOMEM);
blkif->domid = domid;
- atomic_set(&blkif->refcnt, 1);
+ refcount_set(&blkif->refcnt, 1);
init_completion(&blkif->drain_complete);
/*
--
2.7.4
