On Fri, Mar 07, 2025 at 08:47:26PM -0800, Stanislav Fomichev 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.
>
> ndo_setup_tc TC_SETUP_BLOCK
> nft_block_offload_cmd
> nft_chain_offload_cmd
> nft_flow_block_chain
> nft_flow_offload_chain
> nft_flow_rule_offload_abort
> nft_flow_rule_offload_commit
> nft_flow_rule_offload_commit
> nf_tables_commit
> nfnetlink_rcv_batch
> nfnetlink_rcv_skb_batch
> nfnetlink_rcv
> nft_offload_netdev_event
> NETDEV_UNREGISTER notifier
>
> ndo_setup_tc TC_SETUP_FT
> nf_flow_table_offload_cmd
> nf_flow_table_offload_setup
> nft_unregister_flowtable_hook
> nft_register_flowtable_net_hooks
> nft_flowtable_update
> nf_tables_newflowtable
> nfnetlink_rcv_batch (.call NFNL_CB_BATCH)
> nft_flowtable_update
> nf_tables_newflowtable
> nft_flowtable_event
> nf_tables_flowtable_event
> NETDEV_UNREGISTER notifier
> __nft_unregister_flowtable_net_hooks
> nft_unregister_flowtable_net_hooks
> nf_tables_commit
> nfnetlink_rcv_batch (.call NFNL_CB_BATCH)
> __nf_tables_abort
> nf_tables_abort
> nfnetlink_rcv_batch
> __nft_release_hook
> __nft_release_hooks
> nf_tables_pre_exit_net -> module unload
> nft_rcv_nl_event
> netlink_register_notifier (oh boy)
> nft_register_flowtable_net_hooks
> nft_flowtable_update
> nf_tables_newflowtable
> nf_tables_newflowtable
>
> Fixes: c4f0f30b424e ("net: hold netdev instance lock during nft ndo_setup_tc")
> Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxxx>
Thanks Stan,
Thinking aloud: the dev_setup_tc() helper checked if ndo_setup_tc is
non-NULL, but that is not the case here. But that seems ok because it was
also the case prior to the cited commit.
Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
...
