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author | 2017-10-20 10:47:48 +0300 | |
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committer | 2017-10-26 08:36:38 +0200 | |
commit | 0462d9921e3dfcb022600e4db2d67e6ceab57769 (patch) | |
tree | c0574b57bb643f0f21145e1fb9113aeadf6f1b73 /drivers/s390/char/vmur.c | |
parent | s390/cpum_cf: add hardware counter support for IBM z14 (diff) | |
download | linux-0462d9921e3dfcb022600e4db2d67e6ceab57769.tar.gz linux-0462d9921e3dfcb022600e4db2d67e6ceab57769.tar.bz2 linux-0462d9921e3dfcb022600e4db2d67e6ceab57769.zip |
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>
Diffstat (limited to 'drivers/s390/char/vmur.c')
-rw-r--r-- | drivers/s390/char/vmur.c | 8 |
1 files changed, 4 insertions, 4 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; |