VM SIGABRTs on startup if config exceeds certain size

[cedws]

While trying to pass a long environment variable to a VM I found that it will crash immediately on startup if the env var is too long. If the value is 128 bytes it works, but around 1500 bytes it crashes.

These tests demonstrate the issue:

func TestEnvVar(t *testing.T) {
	var (
		shortEnvVar = strings.Repeat("x", 128)
		longEnvVar  = strings.Repeat("x", 1500)
	)

	t.Run("long", func(t *testing.T) {
		_, err := msb.CreateSandbox(
			t.Context(),
			"a134f2dc-1719-45e1-b04f-f79deb4918ae",
			msb.WithCPUs(2),
			msb.WithMemory(1024),
			msb.WithImage("alpine"),
			msb.WithHostname("alpine"),
			msb.WithEnv(map[string]string{
				"x": longEnvVar,
			}),
			msb.WithReplace(),
		)
		if err != nil {
			t.Error("sandbox creation failed:", err)
		}
	})

	t.Run("short", func(t *testing.T) {
		_, err := msb.CreateSandbox(
			t.Context(),
			"a134f2dc-1719-45e1-b04f-f79deb4918ae",
			msb.WithCPUs(2),
			msb.WithMemory(1024),
			msb.WithImage("alpine"),
			msb.WithHostname("alpine"),
			msb.WithEnv(map[string]string{
				"x": shortEnvVar,
			}),
			msb.WithReplace(),
		)
		if err != nil {
			t.Error("sandbox creation failed:", err)
		}
	})
}

msb --version: msb 0.4.5

Go SDK: v0.0.0-20260514032308-b92ec752f916

[toksdotdev]

found out there's an aarch64 limit of ~2kb in contrast to x86_64 which is at 64kb. gonna bump it in libkrunfw.