[PATCH 2/2] host/rootfs: prevent VM ID reuse

Alyssa Ross
2025-12-10T10:55:40Z

Since lsvm ignores empty directories, we can just leave them around to
prevent mktemp -d from reusing the name.

Fixes: b51a97f ("host/rootfs: add run-appimage program")
Signed-off-by: Alyssa Ross <hi@alyssa.is>
---
host/rootfs/image/usr/bin/run-appimage | 7 ++++---
host/rootfs/image/usr/bin/run-flatpak | 7 ++++---
2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/host/rootfs/image/usr/bin/run-appimage b/host/rootfs/image/usr/bin/run-appimage
index d61a79c6..27c6e093 100755
--- a/host/rootfs/image/usr/bin/run-appimage
+++ b/host/rootfs/image/usr/bin/run-appimage
@@ -44,8 +44,9 @@ if { s6-instance-delete /run/service/vm-services $id }
if { umount ${dir}/mount } # mount namespace
if { umount ${dir}/mount } # private bind mount

-# Atomically swap the VM directory with an empty one, which will be ignored by
-# lsvm, then remove it, so we never have half a VM directory.
+# Atomically replace the VM directory with an empty one,
+# which will keep holding the ID so it's not reused,
+# but be ignored by lsvm.
if { mkdir /run/vm/by-id/.${id} }
if { exch /run/vm/by-id/.${id} $dir }
-background { rm -rf /run/vm/by-id/.${id} $dir }
+background { rm -rf /run/vm/by-id/.${id} }
diff --git a/host/rootfs/image/usr/bin/run-flatpak b/host/rootfs/image/usr/bin/run-flatpak
index 6be21075..0cb236f4 100755
--- a/host/rootfs/image/usr/bin/run-flatpak
+++ b/host/rootfs/image/usr/bin/run-flatpak
@@ -46,8 +46,9 @@ if { s6-instance-delete -- /run/service/vm-services $id }
if { umount ${dir}/mount } # mount namespace
if { umount ${dir}/mount } # private bind mount

-# Atomically swap the VM directory with an empty one, which will be ignored by
-# lsvm, then remove it, so we never have half a VM directory.
+# Atomically replace the VM directory with an empty one,
+# which will keep holding the ID so it's not reused,
+# but be ignored by lsvm.
if { mkdir /run/vm/by-id/.${id} }
if { exch /run/vm/by-id/.${id} $dir }
-background { rm -rf /run/vm/by-id/.${id} $dir }
+background { rm -rf /run/vm/by-id/.${id} }
--
2.51.0