act_police: fix a crash during removal

The police action is using its own code to initialize tcf hash
info, which makes us to forgot to initialize a->hinfo correctly.
Fix this by calling the helper function tcf_hash_create() directly.

This patch fixed the following crash:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
IP: [<ffffffff810c099f>] __lock_acquire+0xd3/0xf91
PGD d3c34067 PUD d3e18067 PMD 0
Oops: 0000 [#1] SMP
CPU: 2 PID: 853 Comm: tc Not tainted 4.6.0+ #87
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
task: ffff8800d3e28040 ti: ffff8800d3f6c000 task.ti: ffff8800d3f6c000
RIP: 0010:[<ffffffff810c099f>] [<ffffffff810c099f>] __lock_acquire+0xd3/0xf91
RSP: 0000:ffff88011b203c80 EFLAGS: 00010002
RAX: 0000000000000046 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000028
RBP: ffff88011b203d40 R08: 0000000000000001 R09: 0000000000000000
R10: ffff88011b203d58 R11: ffff88011b208000 R12: 0000000000000001
R13: ffff8800d3e28040 R14: 0000000000000028 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88011b200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000028 CR3: 00000000d4be1000 CR4: 00000000000006e0
Stack:
ffff8800d3e289c0 0000000000000046 000000001b203d60 ffffffff00000000
0000000000000000 ffff880000000000 0000000000000000 ffffffff00000000
ffffffff8187142c ffff88011b203ce8 ffff88011b203ce8 ffffffff8101dbfc
Call Trace:
<IRQ>
[<ffffffff8187142c>] ? __tcf_hash_release+0x77/0xd1
[<ffffffff8101dbfc>] ? native_sched_clock+0x1a/0x35
[<ffffffff8101dbfc>] ? native_sched_clock+0x1a/0x35
[<ffffffff810a9604>] ? sched_clock_local+0x11/0x78
[<ffffffff810bf6a1>] ? mark_lock+0x24/0x201
[<ffffffff810c1dbd>] lock_acquire+0x120/0x1b4
[<ffffffff810c1dbd>] ? lock_acquire+0x120/0x1b4
[<ffffffff8187142c>] ? __tcf_hash_release+0x77/0xd1
[<ffffffff81aad89f>] _raw_spin_lock_bh+0x3c/0x72
[<ffffffff8187142c>] ? __tcf_hash_release+0x77/0xd1
[<ffffffff8187142c>] __tcf_hash_release+0x77/0xd1
[<ffffffff81871a27>] tcf_action_destroy+0x49/0x7c
[<ffffffff81870b1c>] tcf_exts_destroy+0x20/0x2d
[<ffffffff8189273b>] u32_destroy_key+0x1b/0x4d
[<ffffffff81892788>] u32_delete_key_freepf_rcu+0x1b/0x1d
[<ffffffff810de3b8>] rcu_process_callbacks+0x610/0x82e
[<ffffffff8189276d>] ? u32_destroy_key+0x4d/0x4d
[<ffffffff81ab0bc1>] __do_softirq+0x191/0x3f4

Fixes: ddf97ccdd7cb ("net_sched: add network namespace support for tc actions")
Cc: Jamal Hadi Salim <[e-mail]>
Signed-off-by: Cong Wang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/sched/act_police.c

···
 	bool			peak_present;
 };
 #define to_police(pc)	\
-	container_of(pc, struct tcf_police, common)
+	container_of(pc->priv, struct tcf_police, common)
 
 #define POL_TAB_MASK     15
 
···
 				 struct nlattr *est, struct tc_action *a,
 				 int ovr, int bind)
 {
-	unsigned int h;
 	int ret = 0, err;
 	struct nlattr *tb[TCA_POLICE_MAX + 1];
 	struct tc_police *parm;
 	struct tcf_police *police;
 	struct qdisc_rate_table *R_tab = NULL, *P_tab = NULL;
 	struct tc_action_net *tn = net_generic(net, police_net_id);
-	struct tcf_hashinfo *hinfo = tn->hinfo;
 	int size;
 
 	if (nla == NULL)
···
 
 	if (parm->index) {
 		if (tcf_hash_search(tn, a, parm->index)) {
-			police = to_police(a->priv);
+			police = to_police(a);
 			if (bind) {
 				police->tcf_bindcnt += 1;
 				police->tcf_refcnt += 1;
···
 			/* not replacing */
 			return -EEXIST;
 		}
+	} else {
+		ret = tcf_hash_create(tn, parm->index, NULL, a,
+				      sizeof(*police), bind, false);
+		if (ret)
+			return ret;
+		ret = ACT_P_CREATED;
 	}
 
-	police = kzalloc(sizeof(*police), GFP_KERNEL);
-	if (police == NULL)
-		return -ENOMEM;
-	ret = ACT_P_CREATED;
-	police->tcf_refcnt = 1;
-	spin_lock_init(&police->tcf_lock);
-	if (bind)
-		police->tcf_bindcnt = 1;
+	police = to_police(a);
 override:
 	if (parm->rate.rate) {
 		err = -ENOMEM;
···
 		return ret;
 
 	police->tcfp_t_c = ktime_get_ns();
-	police->tcf_index = parm->index ? parm->index :
-		tcf_hash_new_index(tn);
-	police->tcf_tm.install = jiffies;
-	police->tcf_tm.lastuse = jiffies;
-	h = tcf_hash(police->tcf_index, POL_TAB_MASK);
-	spin_lock_bh(&hinfo->lock);
-	hlist_add_head(&police->tcf_head, &hinfo->htab[h]);
-	spin_unlock_bh(&hinfo->lock);
+	tcf_hash_insert(tn, a);
 
-	a->priv = police;
 	return ret;
 
 failure_unlock:
···
 	qdisc_put_rtab(P_tab);
 	qdisc_put_rtab(R_tab);
 	if (ret == ACT_P_CREATED)
-		kfree(police);
+		tcf_hash_cleanup(a, est);
 	return err;
 }