diff options
| author | Elena Reshetova <elena.reshetova@intel.com> | 2017-10-30 14:46:32 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-10-30 15:57:54 -0600 |
| commit | 3b304d24a718ae779ee9c7f2014dd3b2d0893b70 (patch) | |
| tree | 6357ed6aa6ed01c1f81156e8ab9c29c289b85634 /drivers/md/bcache/bcache.h | |
| parent | d59b23795933678c9638fd20c942d2b4f3cd6185 (diff) | |
bcache: convert cached_dev.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 cached_dev.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>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/md/bcache/bcache.h')
| -rw-r--r-- | drivers/md/bcache/bcache.h | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index d77c4829c497..363ea6256b39 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -184,6 +184,7 @@ #include <linux/mutex.h> #include <linux/rbtree.h> #include <linux/rwsem.h> +#include <linux/refcount.h> #include <linux/types.h> #include <linux/workqueue.h> @@ -296,7 +297,7 @@ struct cached_dev { struct semaphore sb_write_mutex; /* Refcount on the cache set. Always nonzero when we're caching. */ - atomic_t count; + refcount_t count; struct work_struct detach; /* @@ -805,13 +806,13 @@ do { \ static inline void cached_dev_put(struct cached_dev *dc) { - if (atomic_dec_and_test(&dc->count)) + if (refcount_dec_and_test(&dc->count)) schedule_work(&dc->detach); } static inline bool cached_dev_get(struct cached_dev *dc) { - if (!atomic_inc_not_zero(&dc->count)) + if (!refcount_inc_not_zero(&dc->count)) return false; /* Paired with the mb in cached_dev_attach */ |