Commit 171526f6 authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Alexei Starovoitov
Browse files

flow_dissector: Pull locking up from prog attach callback 



Split out the part of attach callback that happens with attach/detach lock
acquired. This structures the prog attach callback in a way that opens up
doors for moving the locking out of flow_dissector and into generic
callbacks for attaching/detaching progs to netns in subsequent patches.

Signed-off-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Reviewed-by: default avatarStanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20200531082846.2117903-2-jakub@cloudflare.com
parent febeb6df

net/core/flow_dissector.c

+20 −20
Original line number Diff line number Diff line
@@ -109,15 +109,10 @@ int skb_flow_dissector_prog_query(const union bpf_attr *attr, 
	return 0;

}



int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,

static int flow_dissector_bpf_prog_attach(struct net *net,

					  struct bpf_prog *prog)

{

	struct bpf_prog *attached;

	struct net *net;

	int ret = 0;



	net = current->nsproxy->net_ns;

	mutex_lock(&flow_dissector_mutex);



	if (net == &init_net) {

		/* BPF flow dissector in the root namespace overrides
@@ -130,33 +125,38 @@ int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr, 
		for_each_net(ns) {

			if (ns == &init_net)

				continue;

			if (rcu_access_pointer(ns->flow_dissector_prog)) {

				ret = -EEXIST;

				goto out;

			}

			if (rcu_access_pointer(ns->flow_dissector_prog))

				return -EEXIST;

		}

	} else {

		/* Make sure root flow dissector is not attached

		 * when attaching to the non-root namespace.

		 */

		if (rcu_access_pointer(init_net.flow_dissector_prog)) {

			ret = -EEXIST;

			goto out;

		}

		if (rcu_access_pointer(init_net.flow_dissector_prog))

			return -EEXIST;

	}



	attached = rcu_dereference_protected(net->flow_dissector_prog,

					     lockdep_is_held(&flow_dissector_mutex));

	if (attached == prog) {

	if (attached == prog)

		/* The same program cannot be attached twice */

		ret = -EINVAL;

		goto out;

	}

		return -EINVAL;



	rcu_assign_pointer(net->flow_dissector_prog, prog);

	if (attached)

		bpf_prog_put(attached);

out:

	return 0;

}



int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,

				       struct bpf_prog *prog)

{

	int ret;



	mutex_lock(&flow_dissector_mutex);

	ret = flow_dissector_bpf_prog_attach(current->nsproxy->net_ns, prog);

	mutex_unlock(&flow_dissector_mutex);



	return ret;

}

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