netdev - [PATCH net 1/4] net/sched: act_gact: disallow 'goto chain' on fallback control action

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Message-Id: <02f04ade8a0087781778d02fbb645b1d72f9d777.1540070509.git.dcaratti@redhat.com>
Date:   Sat, 20 Oct 2018 23:33:07 +0200
From:   Davide Caratti <dcaratti@...hat.com>
To:     Jiri Pirko <jiri@...nulli.us>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: [PATCH net 1/4] net/sched: act_gact: disallow 'goto chain' on fallback control action

in the following command:

 # tc action add action <c1> random <rand_type> <c2> <rand_param>

'goto chain x' is allowed only for c1: setting it for c2 makes the kernel
crash with NULL pointer dereference, since TC core doesn't initialize the
chain handle.

Signed-off-by: Davide Caratti <dcaratti@...hat.com>
---
 net/sched/act_gact.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/sched/act_gact.c b/net/sched/act_gact.c
index cd1d9bd32ef9..505138047e5c 100644
--- a/net/sched/act_gact.c
+++ b/net/sched/act_gact.c
@@ -88,6 +88,11 @@ static int tcf_gact_init(struct net *net, struct nlattr *nla,
 		p_parm = nla_data(tb[TCA_GACT_PROB]);
 		if (p_parm->ptype >= MAX_RAND)
 			return -EINVAL;
+		if (TC_ACT_EXT_CMP(p_parm->paction, TC_ACT_GOTO_CHAIN)) {
+			NL_SET_ERR_MSG(extack,
+				       "goto chain not allowed on fallback");
+			return -EINVAL;
+		}
 	}
 #endif
 
-- 
2.17.1