[PATCH] host/rootfs: Sandbox Cloud Hypervisor

[Demi Marie Obenour <demiobenour@gmail.com>]

It only needs access to a small number of resources.  Unfortunately, it
needs access to /dev/vfio right now.  This should be fixed by using file
descriptor passing instead.  Also, Cloud Hypervisor should not run as
root.

Cloud Hypervisor needs to be able to lock memory.  Running in a user
namespace prevents it from using CAP_IPC_LOCK.  Therefore, it is
necessary to increase RLIMIT_MLOCK before running Cloud Hypervisor.

Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
---
 host/rootfs/image/usr/bin/run-vmm | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/host/rootfs/image/usr/bin/run-vmm b/host/rootfs/image/usr/bin/run-vmm
index ba8b59c2677408acdd01c2eda3cf2dd60992d881..24c3d607bfcf6fea6196b61d2941141486d33fd6 100755
--- a/host/rootfs/image/usr/bin/run-vmm
+++ b/host/rootfs/image/usr/bin/run-vmm
@@ -52,5 +52,36 @@ unexport !
 fdmove -c 3 0
 redirfd -r 0 /dev/null
 
+s6-softlimit -H -l 18446744073709551615
 if { udevadm wait /dev/kvm }
-cloud-hypervisor --api-socket fd=3
+bwrap
+  --unshare-all
+  --unshare-user
+  --dev /dev
+  --dev-bind /dev/kvm /dev/kvm
+  --dev-bind /dev/vfio /dev/vfio
+  --tmpfs /dev/shm
+  --tmpfs /tmp
+  --tmpfs /var/tmp
+  --ro-bind /etc /etc
+  --ro-bind /lib /lib
+  --ro-bind /nix /nix
+  --ro-bind /usr /usr
+  --ro-bind /sys /sys
+  --bind /run /run
+  --proc /proc
+  --ro-bind /proc/sys /proc/sys
+  --tmpfs /proc/scsi
+  --remount-ro /proc/scsi
+  --tmpfs /proc/acpi
+  --remount-ro /proc/acpi
+  --tmpfs /proc/fs
+  --remount-ro /proc/fs
+  --tmpfs /proc/irq
+  --remount-ro /proc/irq
+  --ro-bind /dev/null /proc/timer_list
+  --ro-bind /dev/null /proc/kcore
+  --ro-bind /dev/null /proc/kallsyms
+  --ro-bind /dev/null /proc/sysrq-trigger
+  --
+  cloud-hypervisor --api-socket fd=3

---
base-commit: 92e219e7c08c479d216a46d2736ea9d229ff034d
change-id: 20251206-b4-sandbox-9be7e5ed9926

-- 
Sincerely,
Demi Marie Obenour (she/her/hers)