Repository: kubernetes
Issue: Optional secret mounts taint pod directories on host
Labels: kind/bug,sig/storage,lifecycle/stale,needs-triage

### What happened?

1. Create a pod with a volume mount of an optional secret
2. Create the secret
3. Trigger kubelet trying to recreate the container _but not the pod_ 
    - For the repro case I rebooted the VM, but there's probably an easier way to do this
4. Pod now has `CreateContainerConfigError` status and doesn't come up

It looks like what happens is that kubelet creates a directory where it later expects a file:
```
Sep 04 18:05:24 node kubelet[1300]: E0904 18:05:24.448350    1300 kubelet_pods.go:349] "Failed to prepare subPath for volumeMount of the container" err="error creating file /var/lib/kubelet/pods/e32797bd-b956-482c-af31-bffa78ba3ded/volume-subpaths/vol/test/0: open /var/lib/kubelet/pods/e32797bd-b956-482c-af31-bffa78ba3ded/volume-subpaths/vol/test/0: is a directory" containerName="test" volumeMountName="vol"
```
The pod's description says:
```
Error: failed to prepare subPath for volumeMount "vol" of container "test"
```

Restarting the pod (e.g. recreating it, or deleting it if it's in a deployment) solves the problem, because it's a whole new kubelet directory on the host and there is no conflict.

### What did you expect to happen?

I'm not entirely sure if it's reasonable, but I would expect kubelet to detect this provisional directory and delete it first before recreating it now that the secret exists. 

If not, I would at least expect better documentation around this.

### How can we reproduce it (as minimally and precisely as possible)?

Apply this yaml:
```
apiVersion: v1
kind: Pod
metadata:
  name: test
spec:
  tolerations:
    - key: node-role.kubernetes.io/control-plane
      operator: Equal
      effect: NoSchedule

  containers:
  - name: test
    image: busybox:latest
    command: [ "sh", "-c", "sleep infinity" ]
    volumeMounts:
    - mountPath: /run/map/foo
      name: vol
      subPath: foo
  volumes:
    - name: vol
      secret:
        secretName: secret
        optional: true
```
Observe the pod comes up without issue. You can verify the subpath directory is a directory:
```
$ ls -l /var/lib/kubelet/pods/e32797bd-b956-482c-af31-bffa78ba3ded/volume-subpaths/vol/test/
total 4
drwxr-x--- 2 root root 4096 Sep  4 17:59 0
```
Create the secret:
```
$ kubectl create secret generic secret --from-literal=foo=hello
```
Reboot the node/VM.
The pod is now in the error state.
You can also delete and recreate the pod and observe the same directory above is now a file with the expected contents.

### Anything else we need to know?

_No response_

### Kubernetes version

<details>

```console
$ kubectl version
Client Version: v1.31.0
Kustomize Version: v5.4.2
Server Version: v1.31.0
```

</details>


### Cloud provider

N/A


### OS version

<details>

```console
NAME="Ubuntu"
VERSION="20.04.6 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.6 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
```

</details>

### Install tools

kubeadm

### Container runtime (CRI) and version (if applicable)

containerd github.com/containerd/containerd 1.7.12

### Related plugins (CNI, CSI, ...) and versions (if applicable)

N/A