linux-kernel - Re: [RFC PATCH 0/5] allow unprivileged overlay mounts

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Date:   Fri, 25 Oct 2019 08:42:24 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     linux-unionfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/5] allow unprivileged overlay mounts

Miklos Szeredi <mszeredi@...hat.com> writes:

> Hi Eric,
>
> Can you please have a look at this patchset?
>
> The most interesting one is the last oneliner adding FS_USERNS_MOUNT;
> whether I'm correct in stating that this isn't going to introduce any
> holes, or not...

I will take some time and dig through this.

>From a robustness standpoint I worry about the stackable filesystem
side.  As that is uniquely an attack vector with overlayfs.

There is definitely demand for this.


> Thanks,
> Miklos
>
> ---
> Miklos Szeredi (5):
>   ovl: document permission model
>   ovl: ignore failure to copy up unknown xattrs
>   vfs: allow unprivileged whiteout creation
>   ovl: user xattr
>   ovl: unprivieged mounts
>
>  Documentation/filesystems/overlayfs.txt | 44 +++++++++++++
>  fs/char_dev.c                           |  3 +
>  fs/namei.c                              | 17 ++---
>  fs/overlayfs/copy_up.c                  | 34 +++++++---
>  fs/overlayfs/dir.c                      |  2 +-
>  fs/overlayfs/export.c                   |  2 +-
>  fs/overlayfs/inode.c                    | 39 ++++++------
>  fs/overlayfs/namei.c                    | 56 +++++++++--------
>  fs/overlayfs/overlayfs.h                | 81 +++++++++++++++---------
>  fs/overlayfs/ovl_entry.h                |  1 +
>  fs/overlayfs/readdir.c                  |  5 +-
>  fs/overlayfs/super.c                    | 53 +++++++++++-----
>  fs/overlayfs/util.c                     | 82 +++++++++++++++++++++----
>  include/linux/device_cgroup.h           |  3 +
>  14 files changed, 298 insertions(+), 124 deletions(-)

Eric