[PATCH 15/17] fs, btrfs: convert scrub_parity.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 | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 08895d8..4d15112 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -142,7 +142,7 @@ struct scrub_parity {
 
        int                     stripe_len;
 
-       atomic_t                refs;
+       refcount_t              refs;
 
        struct list_head        spages;
 
@@ -2822,12 +2822,12 @@ static inline int scrub_calc_parity_bitmap_len(int 
nsectors)
 
 static void scrub_parity_get(struct scrub_parity *sparity)
 {
-       atomic_inc(&sparity->refs);
+       refcount_inc(&sparity->refs);
 }
 
 static void scrub_parity_put(struct scrub_parity *sparity)
 {
-       if (!atomic_dec_and_test(&sparity->refs))
+       if (!refcount_dec_and_test(&sparity->refs))
                return;
 
        scrub_parity_check_and_repair(sparity);
@@ -2879,7 +2879,7 @@ static noinline_for_stack int scrub_raid56_parity(struct 
scrub_ctx *sctx,
        sparity->scrub_dev = sdev;
        sparity->logic_start = logic_start;
        sparity->logic_end = logic_end;
-       atomic_set(&sparity->refs, 1);
+       refcount_set(&sparity->refs, 1);
        INIT_LIST_HEAD(&sparity->spages);
        sparity->dbitmap = sparity->bitmap;
        sparity->ebitmap = (void *)sparity->bitmap + bitmap_len;
-- 
2.7.4