diff options
| author | Elena Reshetova <elena.reshetova@intel.com> | 2017-10-20 10:47:48 +0300 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-10-26 08:36:38 +0200 |
| commit | 0462d9921e3dfcb022600e4db2d67e6ceab57769 (patch) | |
| tree | c0574b57bb643f0f21145e1fb9113aeadf6f1b73 | |
| parent | 3593eb944c65c7a0adfd679949e67f96d97d1768 (diff) | |
vmur: convert urdev.ref_count from atomic_t to refcount_t
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable urdev.ref_count is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
| -rw-r--r-- | drivers/s390/char/vmur.c | 8 | ||||
| -rw-r--r-- | 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 a50cf930a623..fa90ef05afc0 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); } @@ -945,7 +945,7 @@ 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 fa320ad4593d..35ea9d11d121 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 */ |