CVE-2023-54200

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

netfilter: nf_tables: always release netdev hooks from notifier

This reverts "netfilter: nf_tables: skip netdev events generated on netns removal".

The problem is that when a veth device is released, the veth release

callback will also queue the peer netns device for removal.

Its possible that the peer netns is also slated for removal. In this

case, the device memory is already released before the pre_exit hook of

the peer netns runs:

BUG: KASAN: slab-use-after-free in nf_hook_entry_head+0x1b8/0x1d0

Read of size 8 at addr ffff88812c0124f0 by task kworker/u8:1/45

Workqueue: netns cleanup_net

Call Trace:

nf_hook_entry_head+0x1b8/0x1d0

__nf_unregister_net_hook+0x76/0x510

nft_netdev_unregister_hooks+0xa0/0x220

__nft_release_hook+0x184/0x490

nf_tables_pre_exit_net+0x12f/0x1b0

..

Order is:

1. First netns is released, veth_dellink() queues peer netns device

for removal

2. peer netns is queued for removal

3. peer netns device is released, unreg event is triggered

4. unreg event is ignored because netns is going down

5. pre_exit hook calls nft_netdev_unregister_hooks but device memory

might be free'd already.