[PATCH 18/29] drivers, s390: convert urdev.ref_count from atomic_t to refcount_t

Elena Reshetova
2017-03-06T14:21:05Z

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
---
drivers/s390/char/vmur.c | 8 ++++----
drivers/s390/char/vmur.h | 4 +++-
2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/s390/char/vmur.c b/drivers/s390/char/vmur.c
index 04aceb6..ced8151 100644
--- a/drivers/s390/char/vmur.c
+++ b/drivers/s390/char/vmur.c
@@ -110,7 +110,7 @@ static struct urdev *urdev_alloc(struct ccw_device *cdev)
mutex_init(&urd->io_mutex);
init_waitqueue_head(&urd->wait);
spin_lock_init(&urd->open_lock);
- atomic_set(&urd->ref_count, 1);
+ refcount_set(&urd->ref_count, 1);
urd->cdev = cdev;
get_device(&cdev->dev);
return urd;
@@ -126,7 +126,7 @@ static void urdev_free(struct urdev *urd)

static void urdev_get(struct urdev *urd)
{
- atomic_inc(&urd->ref_count);
+ refcount_inc(&urd->ref_count);
}

static struct urdev *urdev_get_from_cdev(struct ccw_device *cdev)
@@ -159,7 +159,7 @@ static struct urdev *urdev_get_from_devno(u16 devno)

static void urdev_put(struct urdev *urd)
{
- if (atomic_dec_and_test(&urd->ref_count))
+ if (refcount_dec_and_test(&urd->ref_count))
urdev_free(urd);
}

@@ -946,7 +946,7 @@ static int ur_set_offline_force(struct ccw_device *cdev, int force)
rc = -EBUSY;
goto fail_urdev_put;
}
- if (!force && (atomic_read(&urd->ref_count) > 2)) {
+ if (!force && (refcount_read(&urd->ref_count) > 2)) {
/* There is still a user of urd (e.g. ur_open) */
TRACE("ur_set_offline: BUSY\n");
rc = -EBUSY;
diff --git a/drivers/s390/char/vmur.h b/drivers/s390/char/vmur.h
index fa320ad..35ea9d1 100644
--- a/drivers/s390/char/vmur.h
+++ b/drivers/s390/char/vmur.h
@@ -11,6 +11,8 @@
#ifndef _VMUR_H_
#define _VMUR_H_

+#include <linux/refcount.h>
+
#define DEV_CLASS_UR_I 0x20 /* diag210 unit record input device class */
#define DEV_CLASS_UR_O 0x10 /* diag210 unit record output device class */
/*
@@ -69,7 +71,7 @@ struct urdev {
size_t reclen; /* Record length for *write* CCWs */
int class; /* VM device class */
int io_request_rc; /* return code from I/O request */
- atomic_t ref_count; /* reference counter */
+ refcount_t ref_count; /* reference counter */
wait_queue_head_t wait; /* wait queue to serialize open */
int open_flag; /* "urdev is open" flag */
spinlock_t open_lock; /* serialize critical sections */
--
2.7.4

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