[Virtio-fs] [RFC] About non-root virtiofsd(1) process

[Vivek Goyal]

On Tue, Jan 19, 2021 at 08:04:29PM +0530, P J P wrote:
> +-- On Mon, 18 Jan 2021, Stefan Hajnoczi wrote --+
> | Guest applications may run with different uids/gids. The host has no control 
> | over that.
> | 
> | Imagine booting a guest form a virtio-fs root file system and installing 
> | packages. The guest must be able to control uids/gids for that to work.
> 
> * I see; I'll try to better understand how it's done.
> 
> * With UID namespaces, I thought virtiofsd(1) would be able to operate files 
>   with arbitrary uid/gid, even after dropping its root privileges to acquire 
>   non-root privileges on the host; Because it has 'root' privileges under the 
>   shared directory & UID namespace.
> 
> | > $ ./virtiofsd -runas test -o source=...
> | 
> | Patches for this are welcome.
> 
> * Okay, will try.

Catching up with this thread now.

I had posted minimal patches to allow running virtiofsd unpriviliged.
They did not make further progress though.

https://patchew.org/QEMU/20200730194736.173994-1-vgoyal@redhat.com/

While being able to run virtiofsd in a user namespace is certainly
valuable, I feel being able to run virtiofsd unpriviliged has it
use cases as well. For example, if a user wants to share just its
home directory on host with guest. In that case, we probably don't
require lot of priviliged operations to be performed by virtiofsd.

Vivek