[PATCH 01/17] fs, btrfs: convert btrfs_bio.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/volumes.c | 8 ++++----
 fs/btrfs/volumes.h | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b124462..a8fd2e9 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5295,22 +5295,22 @@ static struct btrfs_bio *alloc_btrfs_bio(int 
total_stripes, int real_stripes)
                GFP_NOFS|__GFP_NOFAIL);
 
        atomic_set(&bbio->error, 0);
-       atomic_set(&bbio->refs, 1);
+       refcount_set(&bbio->refs, 1);
 
        return bbio;
 }
 
 void btrfs_get_bbio(struct btrfs_bio *bbio)
 {
-       WARN_ON(!atomic_read(&bbio->refs));
-       atomic_inc(&bbio->refs);
+       WARN_ON(!refcount_read(&bbio->refs));
+       refcount_inc(&bbio->refs);
 }
 
 void btrfs_put_bbio(struct btrfs_bio *bbio)
 {
        if (!bbio)
                return;
-       if (atomic_dec_and_test(&bbio->refs))
+       if (refcount_dec_and_test(&bbio->refs))
                kfree(bbio);
 }
 
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 59be812..ac0bf7d 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -298,7 +298,7 @@ struct btrfs_bio;
 typedef void (btrfs_bio_end_io_t) (struct btrfs_bio *bio, int err);
 
 struct btrfs_bio {
-       atomic_t refs;
+       refcount_t refs;
        atomic_t stripes_pending;
        struct btrfs_fs_info *fs_info;
        u64 map_type; /* get from map_lookup->type */
-- 
2.7.4