linux-kernel - Re: [PATCH] fs/ceph/super: add mount options "snapdir{mode,uid,gid}"

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Message-ID: <CAKPOu+_Jk0EHRDjqiNuFv8wL0kLXLLRZpx7AgWDPOWHzJn22xg@mail.gmail.com>
Date:   Tue, 25 Oct 2022 09:22:59 +0200
From:   Max Kellermann <max.kellermann@...os.com>
To:     Xiubo Li <xiubli@...hat.com>
Cc:     Jeff Layton <jlayton@...nel.org>, idryomov@...il.com,
        ceph-devel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/ceph/super: add mount options "snapdir{mode,uid,gid}"

On Tue, Oct 25, 2022 at 3:36 AM Xiubo Li <xiubli@...hat.com> wrote:
> Currently cephx permission has already supported the 's' permission,
> which means you can do the snapshot create/remove. And for a privileged
> or specific mounts you can give them the 's' permission and then only
> they can do the snapshot create/remove. And all the others won't.

But that's a client permission, not a user permission.

I repeat: the problem is that snapshots should only be
accessible/discoverable/creatable by certain users (UIDs/GIDs) on the
client machine, independent of their permission on the parent
directory.

My patch decouples parent directory permissions from snapdir
permissions, and it's a simple and elegant solution to my problem.

> And then use the container or something else to make the specific users
> could access to them.

Sorry, I don't get it at all. What is "the container or something" and
how does it enable me to prevent specific users from accessing
snapdirs in their home directories?