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Commit b9ca0664 authored by Liu Bo's avatar Liu Bo Committed by Chris Mason
Browse files

Btrfs: do not set subvolume flags in readonly mode 



$ mkfs.btrfs /dev/sdb7
$ btrfstune -S1 /dev/sdb7
$ mount /dev/sdb7 /mnt/btrfs
mount: block device /dev/sdb7 is write-protected, mounting read-only
$ btrfs dev add /dev/sdb8 /mnt/btrfs/

Now we get a btrfs in which mnt flags has readonly but sb flags does
not.  So for those ioctls that only check sb flags with MS_RDONLY, it
is going to be a problem.
Setting subvolume flags is such an ioctl, we should use mnt_want_write_file()
to check RO flags.

Signed-off-by: default avatarLiu Bo <liubo2009@cn.fujitsu.com>
parent e54bfa31

fs/btrfs/ioctl.c

+28 −14
Original line number Diff line number Diff line
@@ -1521,29 +1521,40 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file, 
	u64 flags;

	int ret = 0;



	if (root->fs_info->sb->s_flags & MS_RDONLY)

		return -EROFS;

	ret = mnt_want_write_file(file);

	if (ret)

		goto out;



	if (btrfs_ino(inode) != BTRFS_FIRST_FREE_OBJECTID)

		return -EINVAL;

	if (btrfs_ino(inode) != BTRFS_FIRST_FREE_OBJECTID) {

		ret = -EINVAL;

		goto out_drop_write;

	}



	if (copy_from_user(&flags, arg, sizeof(flags)))

		return -EFAULT;

	if (copy_from_user(&flags, arg, sizeof(flags))) {

		ret = -EFAULT;

		goto out_drop_write;

	}



	if (flags & BTRFS_SUBVOL_CREATE_ASYNC)

		return -EINVAL;

	if (flags & BTRFS_SUBVOL_CREATE_ASYNC) {

		ret = -EINVAL;

		goto out_drop_write;

	}



	if (flags & ~BTRFS_SUBVOL_RDONLY)

		return -EOPNOTSUPP;

	if (flags & ~BTRFS_SUBVOL_RDONLY) {

		ret = -EOPNOTSUPP;

		goto out_drop_write;

	}



	if (!inode_owner_or_capable(inode))

		return -EACCES;

	if (!inode_owner_or_capable(inode)) {

		ret = -EACCES;

		goto out_drop_write;

	}



	down_write(&root->fs_info->subvol_sem);



	/* nothing to do */

	if (!!(flags & BTRFS_SUBVOL_RDONLY) == btrfs_root_readonly(root))

		goto out;

		goto out_drop_sem;



	root_flags = btrfs_root_flags(&root->root_item);

	if (flags & BTRFS_SUBVOL_RDONLY)
@@ -1566,8 +1577,11 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file, 
out_reset:

	if (ret)

		btrfs_set_root_flags(&root->root_item, root_flags);

out:

out_drop_sem:

	up_write(&root->fs_info->subvol_sem);

out_drop_write:

	mnt_drop_write_file(file);

out:

	return ret;

}