Based on the provided code slice and the identified vulnerability (CWE-476: NULL Pointer Dereference) in line 9, here are five possible patches to address the issue:

Patch 1:
```c
if (unlikely(idev && READ_ONCE(idev->cnf.disable_ipv6))) {
```

Patch 2:
```c
if (idev && unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
```

Patch 3:
```c
if (unlikely(idev != NULL && READ_ONCE(idev->cnf.disable_ipv6))) {
```

Patch 4:
```c
if (idev == NULL) {
    return -EINVAL;
}
if (unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
```

Patch 5:
```c
struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb));
if (!idev) {
    IP6_INC_STATS(net, NULL, IPSTATS_MIB_OUTDISCARDS);
    kfree_skb(skb);
    return 0;
}
if (unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
```

These patches aim to check if the `idev` pointer is not NULL before dereferencing it, preventing a potential NULL pointer dereference.