On Sat, Mar 8, 2025 at 5:47 AM Stanislav Fomichev [off-list ref] wrote:

There is a couple of places from which we can arrive to ndo_setup_tc
with TC_SETUP_BLOCK/TC_SETUP_FT:
- netlink
- netlink notifier
- netdev notifier

Locking netdev too deep in this call chain seems to be problematic
(especially assuming some/all of the call_netdevice_notifiers
NETDEV_UNREGISTER) might soon be running with the instance lock).
Revert to lockless ndo_setup_tc for TC_SETUP_BLOCK/TC_SETUP_FT. NFT
framework already takes care of most of the locking. Document
the assumptions.

Fixes: c4f0f30b424e ("net: hold netdev instance lock during nft ndo_setup_tc")
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>

I think you forgot to mention syzbot.

Reported-by: syzbot+0afb4bcf91e5a1afdcad@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/67cb88d1.050a0220.d8275.022d.GAE@google.com/T/#u (local)

Thanks.