Commit 54720df1 authored Mar 12, 2015 by Daniel Borkmann Committed by David S. Miller Mar 12, 2015

cls_bpf: do eBPF invocation under non-bh RCU lock variant for maps



Currently, it is possible in cls_bpf to access eBPF maps only under
rcu_read_lock_bh() variants: while on ingress side, that is, handle_ing(),
the classifier would be called from __netif_receive_skb_core() under
rcu_read_lock(); on egress side, however, it's rcu_read_lock_bh() via
__dev_queue_xmit().

This rcu/rcu_bh mix doesn't work together with eBPF maps as they require
soley to be called under rcu_read_lock(). eBPF maps could also be shared
among various other eBPF programs (possibly even with other eBPF program
types, f.e. tracing) and user space processes, so any context is assumed.

Therefore, a possible fix for cls_bpf is to wrap/nest eBPF program
invocation under non-bh RCU lock variant.

Fixes: e2e9b654 ("cls_bpf: add initial eBPF support for programmable classifiers")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 06741d05

net/sched/cls_bpf.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -64,8 +64,10 @@ static int cls_bpf_classify(struct sk_buff skb, const struct tcf_proto tp,
		{
		struct cls_bpf_head *head = rcu_dereference_bh(tp->root);
		struct cls_bpf_prog *prog;
		int ret;
		int ret = -1;

		/* Needed here for accessing maps. */
		rcu_read_lock();
		list_for_each_entry_rcu(prog, &head->plist, link) {
		int filter_res = BPF_PROG_RUN(prog->filter, skb);

		@@ -80,10 +82,11 @@ static int cls_bpf_classify(struct sk_buff skb, const struct tcf_proto tp,
		if (ret < 0)
		continue;

		return ret;
		break;
		}
		rcu_read_unlock();

		return -1;
		return ret;
		}

		static bool cls_bpf_is_ebpf(const struct cls_bpf_prog *prog)