Re: [PATCH 07/11] fs: Allow CAP_SYS_ADMIN in s_user_ns to freeze and thaw filesystems

[Eric W. Biederman]

Miklos Szeredi <mszeredi@xxxxxxxxxx> writes:

> On Fri, Dec 22, 2017 at 3:32 PM, Dongsu Park <dongsu@xxxxxxxxxx> wrote:
>> From: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
>>
>> The user in control of a super block should be allowed to freeze
>> and thaw it. Relax the restrictions on the FIFREEZE and FITHAW
>> ioctls to require CAP_SYS_ADMIN in s_user_ns.
>
> Why is this required for unprivileged fuse?
>
> Fuse doesn't support freeze, so this seems to make no sense in the
> context of this patchset.

This isn't required to support fuse.  It is a relaxation in permissions
so it isn't strictly necessary for anything.

Until just recently Seth and I work working through the vfs looking at
what we need in general for unprivileged mounts.  With fuse as our focus
but we were not limiting ourselves to fuse.

I have been putting off relaxation of permissions like this because they
are not necessary for safety.  But in general they do make sense.

In practice I think all we need to worry about for fuse is the last 4 patches.


Eric