[PATCH 13/17] fs, btrfs: convert scrub_page.refs from atomic_t to refcount_t

[Elena Reshetova]

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.

Signed-off-by: Elena Reshetova <elena.reshet...@intel.com>
Signed-off-by: Hans Liljestrand <ishkam...@gmail.com>
Signed-off-by: Kees Cook <keesc...@chromium.org>
Signed-off-by: David Windsor <dwind...@gmail.com>
---
 fs/btrfs/scrub.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index c9406bf..8299f64 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -79,7 +79,7 @@ struct scrub_page {
        u64                     logical;
        u64                     physical;
        u64                     physical_for_dev_replace;
-       atomic_t                refs;
+       refcount_t              refs;
        struct {
                unsigned int    mirror_num:8;
                unsigned int    have_csum:1;
@@ -2017,12 +2017,12 @@ static void scrub_block_put(struct scrub_block *sblock)
 
 static void scrub_page_get(struct scrub_page *spage)
 {
-       atomic_inc(&spage->refs);
+       refcount_inc(&spage->refs);
 }
 
 static void scrub_page_put(struct scrub_page *spage)
 {
-       if (atomic_dec_and_test(&spage->refs)) {
+       if (refcount_dec_and_test(&spage->refs)) {
                if (spage->page)
                        __free_page(spage->page);
                kfree(spage);
-- 
2.7.4