From 2a0b4682e09d76466f7b8f5e347ae2ff02f033af Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 10:37:38 +0300 Subject: 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 Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: Mike Snitzer --- drivers/md/dm.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'drivers/md/dm.h') 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 #include #include +#include #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; }; -- cgit