Re: [PATCH v7 15/43] btrfs: implement fscrypt ioctls

[Daniel Vacek]

On Tue, 2 Jun 2026 at 04:37, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
> On Wed, May 13, 2026 at 10:52:49AM +0200, Daniel Vacek wrote:
> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > index 6a37dd3cc5ee..2e0b79f41197 100644
> > --- a/fs/btrfs/ioctl.c
> > +++ b/fs/btrfs/ioctl.c
> > @@ -5159,6 +5159,35 @@ long btrfs_ioctl(struct file *file, unsigned int
> >               return btrfs_ioctl_get_fslabel(fs_info, argp);
> >       case FS_IOC_SETFSLABEL:
> >               return btrfs_ioctl_set_fslabel(file, argp);
> > +#ifdef CONFIG_BTRFS_EXPERIMENTAL
> > +     case FS_IOC_SET_ENCRYPTION_POLICY: {
> > +             if (!IS_ENABLED(CONFIG_FS_ENCRYPTION))
> > +                     return -EOPNOTSUPP;
> > +             if (sb_rdonly(fs_info->sb))
> > +                     return -EROFS;
> > +             /*
> > +              *  If we crash before we commit, nothing encrypted could have
> > +              * been written so it doesn't matter whether the encrypted
> > +              * state persists.
> > +              */
> > +             btrfs_set_fs_incompat(fs_info, ENCRYPT);
> > +             return fscrypt_ioctl_set_policy(file, (const void __user *)arg);
> > +     }
> > +     case FS_IOC_GET_ENCRYPTION_POLICY:
> > +             return fscrypt_ioctl_get_policy(file, (void __user *)arg);
> > +     case FS_IOC_GET_ENCRYPTION_POLICY_EX:
> > +             return fscrypt_ioctl_get_policy_ex(file, (void __user *)arg);
> > +     case FS_IOC_ADD_ENCRYPTION_KEY:
> > +             return fscrypt_ioctl_add_key(file, (void __user *)arg);
> > +     case FS_IOC_REMOVE_ENCRYPTION_KEY:
> > +             return fscrypt_ioctl_remove_key(file, (void __user *)arg);
> > +     case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
> > +             return fscrypt_ioctl_remove_key_all_users(file, (void __user *)arg);
> > +     case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
> > +             return fscrypt_ioctl_get_key_status(file, (void __user *)arg);
> > +     case FS_IOC_GET_ENCRYPTION_NONCE:
> > +             return fscrypt_ioctl_get_nonce(file, (void __user *)arg);
> > +#endif /* CONFIG_BTRFS_EXPERIMENTAL */
>
> Are you sure you want to auto-enable the "encrypt" feature flag like
> this?  It doesn't even require a privilege.
>
> It's also only in FS_IOC_SET_ENCRYPTION_POLICY, so this doesn't work in
> cases where users add a key first.

The filesystem is flagged with encryption once the first file is
encrypted. Adding a key does not change any on-disk data if I'm not
mistaken.

Though I'm open to suggestions.

--nX

> - Eric