btrfs: convert scrub_recover.refs from atomic_t to refcount_t

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.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index b0251eb..c9406bf 100644 (file)
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -64,7 +64,7 @@ struct scrub_ctx;
 #define SCRUB_MAX_PAGES_PER_BLOCK      16      /* 64k per node/leaf/sector */
 
 struct scrub_recover {
-       atomic_t                refs;
+       refcount_t              refs;
        struct btrfs_bio        *bbio;
        u64                     map_length;
 };
@@ -857,12 +857,12 @@ out:
 
 static inline void scrub_get_recover(struct scrub_recover *recover)
 {
-       atomic_inc(&recover->refs);
+       refcount_inc(&recover->refs);
 }
 
 static inline void scrub_put_recover(struct scrub_recover *recover)
 {
-       if (atomic_dec_and_test(&recover->refs)) {
+       if (refcount_dec_and_test(&recover->refs)) {
                btrfs_put_bbio(recover->bbio);
                kfree(recover);
        }
@@ -1343,7 +1343,7 @@ static int scrub_setup_recheck_block(struct scrub_block *original_sblock,
                        return -ENOMEM;
                }
 
-               atomic_set(&recover->refs, 1);
+               refcount_set(&recover->refs, 1);
                recover->bbio = bbio;
                recover->map_length = mapped_length;