btrfs: call permission checks earlier in ioctls and return EPERM

The owner and capability checks in IOC_SUBVOL_SETFLAGS and
SET_RECEIVED_SUBVOL should be called before any other checks are done.

Also unify the error code to EPERM.
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/ioctl.c

@@ -192,6 +192,9 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 	unsigned int i_oldflags;
 	umode_t mode;
 
+	if (!inode_owner_or_capable(inode))
+		return -EPERM;
+
 	if (btrfs_root_readonly(root))
 		return -EROFS;
 
@@ -202,9 +205,6 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 	if (ret)
 		return ret;
 
-	if (!inode_owner_or_capable(inode))
-		return -EACCES;
-
 	ret = mnt_want_write_file(file);
 	if (ret)
 		return ret;
@@ -1697,6 +1697,9 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
 	u64 flags;
 	int ret = 0;
 
+	if (!inode_owner_or_capable(inode))
+		return -EPERM;
+
 	ret = mnt_want_write_file(file);
 	if (ret)
 		goto out;
@@ -1721,11 +1724,6 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
 		goto out_drop_write;
 	}
 
-	if (!inode_owner_or_capable(inode)) {
-		ret = -EACCES;
-		goto out_drop_write;
-	}
-
 	down_write(&root->fs_info->subvol_sem);
 
 	/* nothing to do */
@@ -4403,6 +4401,9 @@ static long btrfs_ioctl_set_received_subvol(struct file *file,
 	int ret = 0;
 	int received_uuid_changed;
 
+	if (!inode_owner_or_capable(inode))
+		return -EPERM;
+
 	ret = mnt_want_write_file(file);
 	if (ret < 0)
 		return ret;
@@ -4419,11 +4420,6 @@ static long btrfs_ioctl_set_received_subvol(struct file *file,
 		goto out;
 	}
 
-	if (!inode_owner_or_capable(inode)) {
-		ret = -EACCES;
-		goto out;
-	}
-
 	sa = memdup_user(arg, sizeof(*sa));
 	if (IS_ERR(sa)) {
 		ret = PTR_ERR(sa);