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:

> s6-supervise can do so directly with less overhead.
>
> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
> ---
>  host/rootfs/file-list.mk                                           | 2 ++
>  .../template/data/service/spectrum-router/flag-newpidns            | 0
>  .../service/vm-services/template/data/service/spectrum-router/run  | 5 ++++-
>  .../vm-services/template/data/service/vhost-user-gpu/flag-newpidns | 0
>  .../service/vm-services/template/data/service/vhost-user-gpu/run   | 7 ++++---
>  5 files changed, 10 insertions(+), 4 deletions(-)

I guess this isn't done for run-vmm because it might not be run through s6?

> diff --git a/host/rootfs/file-list.mk b/host/rootfs/file-list.mk
> index 3899d620717fc97f42e669e5313c4100dcf5b1cd..951cb2e9f0af05839ef5e9c0b5384c13e56622ff 100644
> --- a/host/rootfs/file-list.mk
> +++ b/host/rootfs/file-list.mk
> @@ -30,10 +30,12 @@ FILES = \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/dbus/notification-fd \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/dbus/run \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/down \
> +	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/flag-newpidns \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/notification-fd \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-fs/notification-fd \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-fs/run \
> +	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/flag-newpidns \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/notification-fd \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run \
>  	image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/xdg-desktop-portal-spectrum-host/notification-fd \
> diff --git a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/flag-newpidns b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/flag-newpidns
> new file mode 100644
> index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
> diff --git a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run
> index 3de58c27facc78c48176d8f9a6dd1827ac926f1a..ce84ed951de1a179d1430faae412fe4c1a2fb1f1 100755
> --- a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run
> +++ b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/spectrum-router/run
> @@ -25,7 +25,10 @@ if {
>  s6-setuidgid router
>  
>  bwrap
> -  --unshare-all
> +  --unshare-net
> +  --unshare-ipc
> +  --unshare-uts
> +  --unshare-cgroup
>    --unshare-user
>    --dev-bind / /
>    --setenv RUST_LOG spectrum-router=debug,info
> diff --git a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/flag-newpidns b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/flag-newpidns
> new file mode 100644
> index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
> 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!

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