panic: reflect: slice index out of range in plugins.templateSysData

[Yogeshwar-Pawade]

Summary

json.Marshal inside pkg/plugins.templateSysData (pkg/plugins/common.go:36) panics with reflect: slice index out of range. The panic occurs on a goroutine the executor's DAG runner created (trace below). It is not a fail-stop: the process dies, the rest of the stage is silently skipped, and boot continues.

Affected versions

• v1.25.1 — the version that panicked (used by kairos-io/immucore v0.20.3)
• v1.24.0 — used by kairos-io/kairos-agent v2.29.4; identical code at the same lines
• master, as of 2026-09-24 (latest tag v1.26.4) — still present

Stack trace (excerpt; DAG-runner module path redacted), v1.25.1

panic: reflect: slice index out of range [recovered, repanicked]

goroutine 297 [running]:
reflect.Value.Index({0x..., 0x..., ...}, 0x0)
        reflect/value.go:1424
encoding/json.arrayEncoder.encode(...)
        encoding/json/encode.go:890
encoding/json.sliceEncoder.encode(...)
        encoding/json/encode.go:863
encoding/json.structEncoder.encode(...)
        encoding/json/encode.go:747
encoding/json.ptrEncoder.encode(...)
        encoding/json/encode.go:919
encoding/json.(*encodeState).marshal(...)
        encoding/json/encode.go:343
encoding/json.Marshal(...)
        encoding/json/encode.go:209
github.com/mudler/yip/pkg/plugins.templateSysData(...)
        /go/pkg/mod/github.com/mudler/yip@v1.25.1/pkg/plugins/common.go:36
github.com/mudler/yip/pkg/plugins.IfConditional(...)
        /go/pkg/mod/github.com/mudler/yip@v1.25.1/pkg/plugins/if.go:13
github.com/mudler/yip/pkg/executor.(*DefaultExecutor).applyStage(...)
        /go/pkg/mod/github.com/mudler/yip@v1.25.1/pkg/executor/default.go:82
github.com/mudler/yip/pkg/executor.(*DefaultExecutor).genOpFromSchema.func1(...)
        /go/pkg/mod/github.com/mudler/yip@v1.25.1/pkg/executor/default.go:165
<dag-runner>.(*Graph).Run.func3(...)
        <dag-runner>@v0.4.2/dag.go:159
created by <dag-runner>.(*Graph).Run in goroutine 288
        <dag-runner>@v0.4.2/dag.go:158

Impact

On a host running immucore v0.20.3 (pins yip v1.25.1) the panic fired in the initramfs stage, ~2 of ~25 steps complete:

• immucore.service: Main process exited, code=exited, status=2/INVALIDARGUMENT
• Failed to start immucore. → Dependency failed for Initrd Default Target.
• Boot continued. Because the process exited, the remaining stages — including the one applying the required kernel sysctls (vm.overcommit_memory=1, kernel.panic=10, kernel.panic_on_oops=1) — never ran.
• kubelet then crash-looped under protect-kernel-defaults=true: invalid kernel flag: vm/overcommit_memory, expected value: 1, actual value: 0 / kernel/panic, expected 10 actual 5 / kernel/panic_on_oops, expected 1 actual 0