[PATCH 08/29] drivers, md: convert mddev.active from atomic_t to refcount_t

Elena Reshetova
2017-03-06T14:20:55Z

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/md/md.c | 6 +++---
drivers/md/md.h | 3 ++-
2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 985374f..94c8ebf 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -449,7 +449,7 @@ EXPORT_SYMBOL(md_unplug);

static inline struct mddev *mddev_get(struct mddev *mddev)
{
- atomic_inc(&mddev->active);
+ refcount_inc(&mddev->active);
return mddev;
}

@@ -459,7 +459,7 @@ static void mddev_put(struct mddev *mddev)
{
struct bio_set *bs = NULL;

- if (!atomic_dec_and_lock(&mddev->active, &all_mddevs_lock))
+ if (!refcount_dec_and_lock(&mddev->active, &all_mddevs_lock))
return;
if (!mddev->raid_disks && list_empty(&mddev->disks) &&
mddev->ctime == 0 && !mddev->hold_active) {
@@ -495,7 +495,7 @@ void mddev_init(struct mddev *mddev)
INIT_LIST_HEAD(&mddev->all_mddevs);
setup_timer(&mddev->safemode_timer, md_safemode_timeout,
(unsigned long) mddev);
- atomic_set(&mddev->active, 1);
+ refcount_set(&mddev->active, 1);
atomic_set(&mddev->openers, 0);
atomic_set(&mddev->active_io, 0);
spin_lock_init(&mddev->lock);
diff --git a/drivers/md/md.h b/drivers/md/md.h
index b8859cb..4811663 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -22,6 +22,7 @@
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
+#include <linux/refcount.h>
#include <linux/timer.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
@@ -360,7 +361,7 @@ struct mddev {
*/
struct mutex open_mutex;
struct mutex reconfig_mutex;
- atomic_t active; /* general refcount */
+ refcount_t active; /* general refcount */
atomic_t openers; /* number of active opens */

int changed; /* True if we might need to
--
2.7.4