Commit afec62cd authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

flow_dissector: use RCU protection to fetch dev_net() 



__skb_flow_dissect() can be called from arbitrary contexts.

It must extend its RCU protection section to include
the call to dev_net(), which can become dev_net_rcu().

This makes sure the net structure can not disappear under us.

Fixes: 9b52e3f2 ("flow_dissector: handle no-skb use case")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250205155120.1676781-10-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 4b8474a0

net/core/flow_dissector.c

+11 −10
Original line number Diff line number Diff line
@@ -1108,10 +1108,12 @@ bool __skb_flow_dissect(const struct net *net, 
					      FLOW_DISSECTOR_KEY_BASIC,

					      target_container);



	rcu_read_lock();



	if (skb) {

		if (!net) {

			if (skb->dev)

				net = dev_net(skb->dev);

				net = dev_net_rcu(skb->dev);

			else if (skb->sk)

				net = sock_net(skb->sk);

		}
@@ -1122,7 +1124,6 @@ bool __skb_flow_dissect(const struct net *net, 
		enum netns_bpf_attach_type type = NETNS_BPF_FLOW_DISSECTOR;

		struct bpf_prog_array *run_array;



		rcu_read_lock();

		run_array = rcu_dereference(init_net.bpf.run_array[type]);

		if (!run_array)

			run_array = rcu_dereference(net->bpf.run_array[type]);
@@ -1150,16 +1151,16 @@ bool __skb_flow_dissect(const struct net *net, 
			prog = READ_ONCE(run_array->items[0].prog);

			result = bpf_flow_dissect(prog, &ctx, n_proto, nhoff,

						  hlen, flags);

			if (result == BPF_FLOW_DISSECTOR_CONTINUE)

				goto dissect_continue;

			if (result != BPF_FLOW_DISSECTOR_CONTINUE) {

				__skb_flow_bpf_to_target(&flow_keys, flow_dissector,

							 target_container);

				rcu_read_unlock();

				return result == BPF_OK;

			}

dissect_continue:

		rcu_read_unlock();

		}

	}



	rcu_read_unlock();



	if (dissector_uses_key(flow_dissector,

			       FLOW_DISSECTOR_KEY_ETH_ADDRS)) {