CVE-2024-35839

In the Linux kernel, the following vulnerability has been resolved:
netfilter: bridge: replace physindev with physinif in nf_bridge_info An skb
can be added to a neigh->arp_queue while waiting for an arp reply. Where
original skb’s skb->dev can be different to neigh’s neigh->dev. For
instance in case of bridging dnated skb from one veth to another, the skb
would be added to a neigh->arp_queue of the bridge. As skb->dev can be
reset back to nf_bridge->physindev and used, and as there is no explicit
mechanism that prevents this physindev from been freed under us (for
instance neigh_flush_dev doesn’t cleanup skbs from different device’s neigh
queue) we can crash on e.g. this stack: arp_process neigh_update skb =
__skb_dequeue(&neigh->arp_queue) neigh_resolve_output(…, skb) …
br_nf_dev_xmit br_nf_pre_routing_finish_bridge_slow skb->dev =
nf_bridge->physindev br_handle_frame_finish Let’s use plain ifindex instead
of net_device link. To peek into the original net_device we will use
dev_get_by_index_rcu(). Thus either we get device and are safe to use it or
we don’t get it and drop skb.