CVE-2024-42108 Information

Description

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.

Reference

https://git.kernel.org/stable/c/92cbbe7759193e3418f38d0d73f8fe125312c58b https://git.kernel.org/stable/c/9a0c28efeec6383ef22e97437616b920e7320b67