CVE-2024-42108

In the Linux kernel, the following vulnerability has been resolved:

net: rswitch: Avoid use-after-free in rswitch_poll()

The use-after-free is actually in rswitch_tx_free(), which is inlined in

rswitch_poll(). Since `skb` and `gq->skbs[gq->dirty]` are in fact the

same pointer, the skb is first freed using dev_kfree_skb_any(), then the

value in skb->len is used to update the interface statistics.

Let's move around the instructions to use skb->len before the skb is

freed.

This bug is trivial to reproduce using KFENCE. It will trigger a splat

every few packets. A simple ARP request or ICMP echo request is enough.