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    SubjectRe: [PATCH 08/29] drivers, md: convert mddev.active from atomic_t to refcount_t
    On Mon, Mar 06, 2017 at 04:20:55PM +0200, Elena Reshetova wrote:
    > 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.

    Looks good. Let me know how do you want to route the patch to upstream.

    > 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
    >
    > --
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