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

[Davide Caratti]

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 <dcara...@redhat.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