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

["Reshetova, Elena" <elena.reshetova@xxxxxxxxx>]

> 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.

Greg, you previously mentioned that driver's conversions can go via your tree. 
Does this still apply?
Or should I be asking maintainers to merge these patches via their trees? 
I am not sure about the correct (and easier for everyone) way, please suggest.  

Best Regards,
Elena.
> 
> > Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
> > Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
> > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>
> > ---
> >  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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