Re: [PATCH v2 3/3] virtiofsd: probe unshare(CLONE_FS) and print an error

[Daniel Walsh]

On 7/28/20 11:32, Stefan Hajnoczi wrote:
> On Tue, Jul 28, 2020 at 12:00:20PM +0200, Roman Mohr wrote:
>> On Tue, Jul 28, 2020 at 3:07 AM misono.tomohiro@fujitsu.com <
>> misono.tomohiro@fujitsu.com> wrote:
>>
>>>> Subject: [PATCH v2 3/3] virtiofsd: probe unshare(CLONE_FS) and print an
>>> error
>>>> An assertion failure is raised during request processing if
>>>> unshare(CLONE_FS) fails. Implement a probe at startup so the problem can
>>>> be detected right away.
>>>>
>>>> Unfortunately Docker/Moby does not include unshare in the seccomp.json
>>>> list unless CAP_SYS_ADMIN is given. Other seccomp.json lists always
>>>> include unshare (e.g. podman is unaffected):
>>>>
>>> https://raw.githubusercontent.com/seccomp/containers-golang/master/seccomp.json
>>>> Use "docker run --security-opt seccomp=path/to/seccomp.json ..." if the
>>>> default seccomp.json is missing unshare.
>>> Hi, sorry for a bit late.
>>>
>>> unshare() was added to fix xattr problem:
>>>
>>> https://github.com/qemu/qemu/commit/bdfd66788349acc43cd3f1298718ad491663cfcc#
>>> In theory we don't need to call unshare if xattr is disabled, but it is
>>> hard to get to know
>>> if xattr is enabled or disabled in fv_queue_worker(), right?
>>>
>>>
>> In kubevirt we want to run virtiofsd in containers. We would already not
>> have xattr support for e.g. overlayfs in the VM after this patch series (an
>> acceptable con at least for us right now).
>> If we can get rid of the unshare (and potentially of needing root) that
>> would be great. We always assume that everything which we run in containers
>> should work for cri-o and docker.
> Root is required to access files with any uid/gid.
>
> Dave Gilbert is working on xattr support without CAP_SYS_ADMIN. He may
> be able to find a way to drop unshare (at least in containers).
>
>> "Just" pointing docker to a different seccomp.json file is something which
>> k8s users/admin in many cases can't do.
> There is a Moby PR to change the default seccomp.json file here but it's
> unclear if it will be merged:
> https://github.com/moby/moby/pull/41244
>
> Stefan

Why not try Podman?

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