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fix(firecracker): VMs outlived their runs and snapshots #52

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Merged
chxmxii merged 1 commit into from
Oct 12, 2026
Merged

fix(firecracker): VMs outlived their runs and snapshots #52

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8 changes: 8 additions & 0 deletions internal/runtime/unshare.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,14 @@ import (
// pause process exists. The environment podman unshare would set is set the
// same way, so helpers that check for it behave identically.
func inPodmanNS(argv ...string) *exec.Cmd {
// Already inside it -- `box __fc` and the other helpers run there --
// the namespace cannot be entered again: setns into the user namespace
// one is in fails with EINVAL. Run argv directly. Without this, a
// Firecracker VM torn down from inside never got its crun kill, and every
// run and snapshot left its VM running.
if os.Getenv("_CONTAINERS_USERNS_CONFIGURED") != "" {
return exec.Command(argv[0], argv[1:]...)
}
if pid := pausePID(); pid > 0 {
args := []string{"--user", "--mount", "--preserve-credentials", "--target", strconv.Itoa(pid), "--"}
cmd := exec.Command("nsenter", append(args, argv...)...)
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12 changes: 12 additions & 0 deletions security/escape-test.sh
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Expand Up @@ -261,6 +261,18 @@ t0=$(date +%s%N); ls / >/dev/null; t1=$(date +%s%N)
[ $(( (t1 - t0) / 1000000 )) -lt 1000 ] && pass "host responsive during a guest fork bomb" \
|| fail "host slowed by a guest fork bomb"

echo
echo "nothing left behind"
# A run's VM is gone when the run is; only the sandbox that is up stays.
"$BB" run "$NAME" -- true >/dev/null 2>&1
sleep 1
case "$BACKEND" in
firecracker) left=$(podman unshare crun --root "${XDG_RUNTIME_DIR:-/tmp}/box/fc" list 2>/dev/null | awk -v up="box-up-$NAME" 'NR>1 && $1 ~ /^box-/ && $1 != up' | wc -l) ;;
krun) left=$(podman unshare krun --root "${XDG_RUNTIME_DIR:-/tmp}/box/krun" list 2>/dev/null | awk -v up="box-up-$NAME" 'NR>1 && $1 ~ /^box-/ && $1 != up' | wc -l) ;;
*) left=$(podman ps -a --format '{{.Names}}' 2>/dev/null | grep "^box-$NAME-" | wc -l) ;;
esac
[ "$left" -eq 0 ] && pass "no VM outlives its run" || fail "$left VM(s) still running after their run ended"

echo
if [ "$FAILS" -eq 0 ]; then
echo "no escapes."
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