btrfs: convert btrfs_delayed_item.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/delayed-inode.c b/fs/btrfs/delayed-inode.c
index 7396c36..8ae409b 100644 (file)
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -308,7 +308,7 @@ static struct btrfs_delayed_item *btrfs_alloc_delayed_item(u32 data_len)
                item->ins_or_del = 0;
                item->bytes_reserved = 0;
                item->delayed_node = NULL;
-               atomic_set(&item->refs, 1);
+               refcount_set(&item->refs, 1);
        }
        return item;
 }
@@ -483,7 +483,7 @@ static void btrfs_release_delayed_item(struct btrfs_delayed_item *item)
 {
        if (item) {
                __btrfs_remove_delayed_item(item);
-               if (atomic_dec_and_test(&item->refs))
+               if (refcount_dec_and_test(&item->refs))
                        kfree(item);
        }
 }
@@ -1600,14 +1600,14 @@ bool btrfs_readdir_get_delayed_items(struct inode *inode,
        mutex_lock(&delayed_node->mutex);
        item = __btrfs_first_delayed_insertion_item(delayed_node);
        while (item) {
-               atomic_inc(&item->refs);
+               refcount_inc(&item->refs);
                list_add_tail(&item->readdir_list, ins_list);
                item = __btrfs_next_delayed_item(item);
        }
 
        item = __btrfs_first_delayed_deletion_item(delayed_node);
        while (item) {
-               atomic_inc(&item->refs);
+               refcount_inc(&item->refs);
                list_add_tail(&item->readdir_list, del_list);
                item = __btrfs_next_delayed_item(item);
        }
@@ -1634,13 +1634,13 @@ void btrfs_readdir_put_delayed_items(struct inode *inode,
 
        list_for_each_entry_safe(curr, next, ins_list, readdir_list) {
                list_del(&curr->readdir_list);
-               if (atomic_dec_and_test(&curr->refs))
+               if (refcount_dec_and_test(&curr->refs))
                        kfree(curr);
        }
 
        list_for_each_entry_safe(curr, next, del_list, readdir_list) {
                list_del(&curr->readdir_list);
-               if (atomic_dec_and_test(&curr->refs))
+               if (refcount_dec_and_test(&curr->refs))
                        kfree(curr);
        }
 
@@ -1667,7 +1667,7 @@ int btrfs_should_delete_dir_index(struct list_head *del_list,
                list_del(&curr->readdir_list);
                ret = (curr->key.offset == index);
 
-               if (atomic_dec_and_test(&curr->refs))
+               if (refcount_dec_and_test(&curr->refs))
                        kfree(curr);
 
                if (ret)
@@ -1705,7 +1705,7 @@ int btrfs_readdir_delayed_dir_index(struct dir_context *ctx,
                list_del(&curr->readdir_list);
 
                if (curr->key.offset < ctx->pos) {
-                       if (atomic_dec_and_test(&curr->refs))
+                       if (refcount_dec_and_test(&curr->refs))
                                kfree(curr);
                        continue;
                }
@@ -1722,7 +1722,7 @@ int btrfs_readdir_delayed_dir_index(struct dir_context *ctx,
                over = !dir_emit(ctx, name, name_len,
                               location.objectid, d_type);
 
-               if (atomic_dec_and_test(&curr->refs))
+               if (refcount_dec_and_test(&curr->refs))
                        kfree(curr);
 
                if (over)

diff --git a/fs/btrfs/delayed-inode.h b/fs/btrfs/delayed-inode.h
index 2f494fd..c4189d4 100644 (file)
--- a/fs/btrfs/delayed-inode.h
+++ b/fs/btrfs/delayed-inode.h
@@ -80,7 +80,7 @@ struct btrfs_delayed_item {
        struct list_head readdir_list;  /* used for readdir items */
        u64 bytes_reserved;
        struct btrfs_delayed_node *delayed_node;
-       atomic_t refs;
+       refcount_t refs;
        int ins_or_del;
        u32 data_len;
        char data[0];