Re: [PATCH] host/rootfs: Avoid using bwrap to enter new PID namespace

[Alyssa Ross <hi@alyssa.is>]

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Demi Marie Obenour <demiobenour@gmail.com> writes:

> On 7/13/26 05:01, Alyssa Ross wrote:
>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>> 
>>> On 7/10/26 10:39, Alyssa Ross wrote:
>>>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>>>>
>>>>> diff --git a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run
>>>>> index c3bfafe02ec6d2ee418fe56b033bbc4c7a73b186..f5c0f15184f0e72457f9c0bfa546590b9308eb9c 100755
>>>>> --- a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run
>>>>> +++ b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run
>>>>> @@ -17,9 +17,10 @@ s6-applyuidgid -UzG 15 # wayland
>>>>>  s6-ipcserverd -1c 1
>>>>>  
>>>>>  bwrap
>>>>> -  --unshare-all
>>>>> -  # --unshare-all only implies --unshare-user-try.
>>>>> -  # Make this more than a "try".
>>>>> +  --unshare-net
>>>>> +  --unshare-ipc
>>>>> +  --unshare-uts
>>>>> +  --unshare-cgroup
>>>>>    --unshare-user
>>>>>    --bind $WAYLAND_DISPLAY $WAYLAND_DISPLAY
>>>>>    --ro-bind /usr /usr
>>>>
>>>> There's a subtle behaviour change here.  The pid namespace is reused
>>>> between runs of crosvm, because if crosvm exits, s6-ipcserverd will stay
>>>> running and wait for the next connection, then respawn crosvm.  It's
>>>> done this way because crosvm has made the unusual decision to support
>>>> being started on a connected socket, rather than a listening socket like
>>>> one might expect.  Is that okay?  I'd guess yes, but I want to check
>>>> with you!
>>>
>>> It's less robust than I would like, but there is no reason one cannot
>>> have both s6-supervise and bubblewrap create PID namespaces.  That's
>>> the approach I would go with.
>> 
>> What's the point of the intermediate PID namespace?
>
> Ensure that there are no stale Cloud Hypervisor processes left behind.
> Specifically, the PTY watcher ought to be moved to the main process
> if there is only one PTY, but it’s currently a separate process.

Huh?  This is a discussion about the vhost-user-gpu service, which runs
crosvm via s6-ipcserver.  Cloud Hypervisor and PTY watchers are not
involved.

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