[PATCH net] net: sched: set xt_tgchk_param par.net properly in ipt_init_target

Now xt_tgchk_param par in ipt_init_target is a local varibale,
par.net is not initialized there. Later when xt_check_target
calls target's checkentry in which it may access par.net, it
would cause kernel panic.

Jaroslav found this panic when running:

  # ip link add TestIface type dummy
  # tc qd add dev TestIface ingress handle ffff:
  # tc filter add dev TestIface parent ffff: u32 match u32 0 0 \
    action xt -j CONNMARK --set-mark 4

This patch is to pass net param into ipt_init_target and set
par.net with it properly in there.

Reported-by: Jaroslav Aster <redacted>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 net/sched/act_ipt.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/net/sched/act_ipt.c b/net/sched/act_ipt.c
index 36f0ced..bb06d2ed 100644
--- a/net/sched/act_ipt.c
+++ b/net/sched/act_ipt.c

@@ -36,8 +36,8 @@ static struct tc_action_ops act_ipt_ops;
 static unsigned int xt_net_id;
 static struct tc_action_ops act_xt_ops;
 
-static int ipt_init_target(struct xt_entry_target *t, char *table,
-			   unsigned int hook)
+static int ipt_init_target(struct net *net, struct xt_entry_target *t,
+			   char *table, unsigned int hook)
 {
 	struct xt_tgchk_param par;
 	struct xt_target *target;

@@ -49,6 +49,7 @@ static int ipt_init_target(struct xt_entry_target *t, char *table,
 		return PTR_ERR(target);
 
 	t->u.kernel.target = target;
+	par.net       = net;
 	par.table     = table;
 	par.entryinfo = NULL;
 	par.target    = target;

@@ -91,10 +92,11 @@ static const struct nla_policy ipt_policy[TCA_IPT_MAX + 1] = {
 	[TCA_IPT_TARG]	= { .len = sizeof(struct xt_entry_target) },
 };
 
-static int __tcf_ipt_init(struct tc_action_net *tn, struct nlattr *nla,
+static int __tcf_ipt_init(struct net *net, struct nlattr *nla,
 			  struct nlattr *est, struct tc_action **a,
 			  const struct tc_action_ops *ops, int ovr, int bind)
 {
+	struct tc_action_net *tn = net_generic(net, xt_net_id);
 	struct nlattr *tb[TCA_IPT_MAX + 1];
 	struct tcf_ipt *ipt;
 	struct xt_entry_target *td, *t;

@@ -159,7 +161,7 @@ static int __tcf_ipt_init(struct tc_action_net *tn, struct nlattr *nla,
 	if (unlikely(!t))
 		goto err2;
 
-	err = ipt_init_target(t, tname, hook);
+	err = ipt_init_target(net, t, tname, hook);
 	if (err < 0)
 		goto err3;
 

@@ -193,18 +195,14 @@ static int tcf_ipt_init(struct net *net, struct nlattr *nla,
 			struct nlattr *est, struct tc_action **a, int ovr,
 			int bind)
 {
-	struct tc_action_net *tn = net_generic(net, ipt_net_id);
-
-	return __tcf_ipt_init(tn, nla, est, a, &act_ipt_ops, ovr, bind);
+	return __tcf_ipt_init(net, nla, est, a, &act_ipt_ops, ovr, bind);
 }
 
 static int tcf_xt_init(struct net *net, struct nlattr *nla,
 		       struct nlattr *est, struct tc_action **a, int ovr,
 		       int bind)
 {
-	struct tc_action_net *tn = net_generic(net, xt_net_id);
-
-	return __tcf_ipt_init(tn, nla, est, a, &act_xt_ops, ovr, bind);
+	return __tcf_ipt_init(net, nla, est, a, &act_xt_ops, ovr, bind);
 }
 
 static int tcf_ipt(struct sk_buff *skb, const struct tc_action *a,

-- 
2.1.0

On Sat, Aug 5, 2017 at 1:48 AM, Xin Long [off-list ref] wrote:

...

This is not correct.

You miss ipt_net_id != xt_net_id.

On Tue, Aug 8, 2017 at 9:00 AM, Cong Wang [off-list ref] wrote:

On Sat, Aug 5, 2017 at 1:48 AM, Xin Long [off-list ref] wrote:

quoted

-static int __tcf_ipt_init(struct tc_action_net *tn, struct nlattr *nla,
+static int __tcf_ipt_init(struct net *net, struct nlattr *nla,
                          struct nlattr *est, struct tc_action **a,
                          const struct tc_action_ops *ops, int ovr, int bind)
 {
+       struct tc_action_net *tn = net_generic(net, xt_net_id);

...

quoted

@@ -193,18 +195,14 @@ static int tcf_ipt_init(struct net *net, struct nlattr *nla,
                        struct nlattr *est, struct tc_action **a, int ovr,
                        int bind)
 {
-       struct tc_action_net *tn = net_generic(net, ipt_net_id);
-
-       return __tcf_ipt_init(tn, nla, est, a, &act_ipt_ops, ovr, bind);
+       return __tcf_ipt_init(net, nla, est, a, &act_ipt_ops, ovr, bind);
 }

 static int tcf_xt_init(struct net *net, struct nlattr *nla,
                       struct nlattr *est, struct tc_action **a, int ovr,
                       int bind)
 {
-       struct tc_action_net *tn = net_generic(net, xt_net_id);
-
-       return __tcf_ipt_init(tn, nla, est, a, &act_xt_ops, ovr, bind);
+       return __tcf_ipt_init(net, nla, est, a, &act_xt_ops, ovr, bind);

This is not correct.

You miss ipt_net_id != xt_net_id.

right, that's a silly mistake. seems no better way but to pass both
net and net_id to __tcf_ipt_init. will send v2. thanks.