btrfs: convert btrfs_raid_bio.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/raid56.c b/fs/btrfs/raid56.c
index 1571bf26dc077a0575b39977ead28e229d68550f..a8954f5188b4d8a6e064ea84d2f214c9ced6a251 100644 (file)
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -149,7 +149,7 @@ struct btrfs_raid_bio {
 
        int generic_bio_cnt;
 
-       atomic_t refs;
+       refcount_t refs;
 
        atomic_t stripes_pending;
 
@@ -389,7 +389,7 @@ static void __remove_rbio_from_cache(struct btrfs_raid_bio *rbio)
                if (bio_list_empty(&rbio->bio_list)) {
                        if (!list_empty(&rbio->hash_list)) {
                                list_del_init(&rbio->hash_list);
-                               atomic_dec(&rbio->refs);
+                               refcount_dec(&rbio->refs);
                                BUG_ON(!list_empty(&rbio->plug_list));
                        }
                }
@@ -480,7 +480,7 @@ static void cache_rbio(struct btrfs_raid_bio *rbio)
 
        /* bump our ref if we were not in the list before */
        if (!test_and_set_bit(RBIO_CACHE_BIT, &rbio->flags))
-               atomic_inc(&rbio->refs);
+               refcount_inc(&rbio->refs);
 
        if (!list_empty(&rbio->stripe_cache)){
                list_move(&rbio->stripe_cache, &table->stripe_cache);
@@ -689,7 +689,7 @@ static noinline int lock_stripe_add(struct btrfs_raid_bio *rbio)
                            test_bit(RBIO_CACHE_BIT, &cur->flags) &&
                            !test_bit(RBIO_RMW_LOCKED_BIT, &cur->flags)) {
                                list_del_init(&cur->hash_list);
-                               atomic_dec(&cur->refs);
+                               refcount_dec(&cur->refs);
 
                                steal_rbio(cur, rbio);
                                cache_drop = cur;
@@ -738,7 +738,7 @@ static noinline int lock_stripe_add(struct btrfs_raid_bio *rbio)
                }
        }
 lockit:
-       atomic_inc(&rbio->refs);
+       refcount_inc(&rbio->refs);
        list_add(&rbio->hash_list, &h->hash_list);
 out:
        spin_unlock_irqrestore(&h->lock, flags);
@@ -784,7 +784,7 @@ static noinline void unlock_stripe(struct btrfs_raid_bio *rbio)
                }
 
                list_del_init(&rbio->hash_list);
-               atomic_dec(&rbio->refs);
+               refcount_dec(&rbio->refs);
 
                /*
                 * we use the plug list to hold all the rbios
@@ -801,7 +801,7 @@ static noinline void unlock_stripe(struct btrfs_raid_bio *rbio)
                        list_del_init(&rbio->plug_list);
 
                        list_add(&next->hash_list, &h->hash_list);
-                       atomic_inc(&next->refs);
+                       refcount_inc(&next->refs);
                        spin_unlock(&rbio->bio_list_lock);
                        spin_unlock_irqrestore(&h->lock, flags);
 
@@ -843,8 +843,7 @@ static void __free_raid_bio(struct btrfs_raid_bio *rbio)
 {
        int i;
 
-       WARN_ON(atomic_read(&rbio->refs) < 0);
-       if (!atomic_dec_and_test(&rbio->refs))
+       if (!refcount_dec_and_test(&rbio->refs))
                return;
 
        WARN_ON(!list_empty(&rbio->stripe_cache));
@@ -997,7 +996,7 @@ static struct btrfs_raid_bio *alloc_rbio(struct btrfs_fs_info *fs_info,
        rbio->stripe_npages = stripe_npages;
        rbio->faila = -1;
        rbio->failb = -1;
-       atomic_set(&rbio->refs, 1);
+       refcount_set(&rbio->refs, 1);
        atomic_set(&rbio->error, 0);
        atomic_set(&rbio->stripes_pending, 0);