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authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 10:37:38 +0300
committerMike Snitzer <snitzer@redhat.com>2017-10-24 15:09:51 -0400
commit2a0b4682e09d76466f7b8f5e347ae2ff02f033af (patch)
tree1f54fee8c0178790f22468e64f8b2984ffe828de /drivers/md/dm.h
parentbb176f67090ca54869fc1262c913aa69d2ede070 (diff)
downloadlinux-2a0b4682e09d76466f7b8f5e347ae2ff02f033af.tar.bz2
dm: convert dm_dev_internal.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 dm_dev_internal.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: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm.h')
-rw-r--r--drivers/md/dm.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 38c84c0a35d4..36399bb875dd 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -19,6 +19,7 @@
#include <linux/hdreg.h>
#include <linux/completion.h>
#include <linux/kobject.h>
+#include <linux/refcount.h>
#include "dm-stats.h"
@@ -38,7 +39,7 @@
*/
struct dm_dev_internal {
struct list_head list;
- atomic_t count;
+ refcount_t count;
struct dm_dev *dm_dev;
};