netdev - [PATCH net-next v3 1/5] tc/act: user space can't use TC_ACT

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Message-Id: <82c5852909788fef3c7b5c29d6ad8c90b60c7170.1532437050.git.pabeni@redhat.com>
Date:   Tue, 24 Jul 2018 22:06:39 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Daniel Borkmann <daniel@...earbox.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Eyal Birger <eyal.birger@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH net-next v3 1/5] tc/act: user space can't use TC_ACT_REDIRECT directly

Only cls_bpf and act_bpf can safely use such value. If a generic
action is configured by user space to return TC_ACT_REDIRECT,
the usually visible behavior is passing the skb up the stack - as
for unknown action, but, with complex configuration, more random
results can be obtained.

This patch forcefully converts TC_ACT_REDIRECT to TC_ACT_UNSPEC
at action init time, making the kernel behavior more consistent.

v1 -> v3: use TC_ACT_UNSPEC instead of a newly definied act value

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/sched/act_api.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 148a89ab789b..24b5534967fe 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -895,6 +895,11 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
 		}
 	}
 
+	if (a->tcfa_action == TC_ACT_REDIRECT) {
+		net_warn_ratelimited("TC_ACT_REDIRECT can't be used directly");
+		a->tcfa_action = TC_ACT_UNSPEC;
+	}
+
 	return a;
 
 err_mod:
-- 
2.17.1