bridge: fix some kernel warning in multicast timer

Several people reported the warning: "kernel BUG at kernel/timer.c:729!"
and the stack trace is:

	#7 [ffff880214d25c10] mod_timer+501 at ffffffff8106d905
	#8 [ffff880214d25c50] br_multicast_del_pg.isra.20+261 at ffffffffa0731d25 [bridge]
	#9 [ffff880214d25c80] br_multicast_disable_port+88 at ffffffffa0732948 [bridge]
	#10 [ffff880214d25cb0] br_stp_disable_port+154 at ffffffffa072bcca [bridge]
	#11 [ffff880214d25ce8] br_device_event+520 at ffffffffa072a4e8 [bridge]
	#12 [ffff880214d25d18] notifier_call_chain+76 at ffffffff8164aafc
	#13 [ffff880214d25d50] raw_notifier_call_chain+22 at ffffffff810858f6
	#14 [ffff880214d25d60] call_netdevice_notifiers+45 at ffffffff81536aad
	#15 [ffff880214d25d80] dev_close_many+183 at ffffffff81536d17
	#16 [ffff880214d25dc0] rollback_registered_many+168 at ffffffff81537f68
	#17 [ffff880214d25de8] rollback_registered+49 at ffffffff81538101
	#18 [ffff880214d25e10] unregister_netdevice_queue+72 at ffffffff815390d8
	#19 [ffff880214d25e30] __tun_detach+272 at ffffffffa074c2f0 [tun]
	#20 [ffff880214d25e88] tun_chr_close+45 at ffffffffa074c4bd [tun]
	#21 [ffff880214d25ea8] __fput+225 at ffffffff8119b1f1
	#22 [ffff880214d25ef0] ____fput+14 at ffffffff8119b3fe
	#23 [ffff880214d25f00] task_work_run+159 at ffffffff8107cf7f
	#24 [ffff880214d25f30] do_notify_resume+97 at ffffffff810139e1
	#25 [ffff880214d25f50] int_signal+18 at ffffffff8164f292

this is due to I forgot to check if mp->timer is armed in
br_multicast_del_pg(). This bug is introduced by
commit 9f00b2e7cf241fa389733d41b6 (bridge: only expire the mdb entry
when query is received).

Same for __br_mdb_del().

Tested-by: poma <pomidorabelisima@gmail.com>
Reported-by: LiYonghua <809674045@qq.com>
Reported-by: Robert Hancock <hancockrwd@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static int br_ip6_multicast_mld2_report(struct net_bridge *br,
					struct net_bridge_port *port,
					struct sk_buff *skb)
{
	struct icmp6hdr *icmp6h;
	struct mld2_grec *grec;
	int i;
	int len;
	int num;
	int err = 0;
	u16 vid = 0;

	if (!pskb_may_pull(skb, sizeof(*icmp6h)))
		return -EINVAL;

	br_vlan_get_tag(skb, &vid);
	icmp6h = icmp6_hdr(skb);
	num = ntohs(icmp6h->icmp6_dataun.un_data16[1]);
	len = sizeof(*icmp6h);

	for (i = 0; i < num; i++) {
		__be16 *nsrcs, _nsrcs;

		nsrcs = skb_header_pointer(skb,
					   len + offsetof(struct mld2_grec,
							  grec_nsrcs),
					   sizeof(_nsrcs), &_nsrcs);
		if (!nsrcs)
			return -EINVAL;

		if (!pskb_may_pull(skb,
				   len + sizeof(*grec) +
				   sizeof(struct in6_addr) * ntohs(*nsrcs)))
			return -EINVAL;

		grec = (struct mld2_grec *)(skb->data + len);
		len += sizeof(*grec) +
		       sizeof(struct in6_addr) * ntohs(*nsrcs);

		/* We treat these as MLDv1 reports for now. */
		switch (grec->grec_type) {
		case MLD2_MODE_IS_INCLUDE:
		case MLD2_MODE_IS_EXCLUDE:
		case MLD2_CHANGE_TO_INCLUDE:
		case MLD2_CHANGE_TO_EXCLUDE:
		case MLD2_ALLOW_NEW_SOURCES:
		case MLD2_BLOCK_OLD_SOURCES:
			break;

		default:
			continue;
		}

		err = br_ip6_multicast_add_group(br, port, &grec->grec_mca,
						 vid);
		if (!err)
			break;
	}

	return err;
}

static int br_ip6_multicast_mld2_report(struct net_bridge *br,
					struct net_bridge_port *port,
					struct sk_buff *skb)
{
	struct icmp6hdr *icmp6h;
	struct mld2_grec *grec;
	int i;
	int len;
	int num;
	int err = 0;
	u16 vid = 0;

	if (!pskb_may_pull(skb, sizeof(*icmp6h)))
		return -EINVAL;

	br_vlan_get_tag(skb, &vid);
	icmp6h = icmp6_hdr(skb);
	num = ntohs(icmp6h->icmp6_dataun.un_data16[1]);
	len = sizeof(*icmp6h);

	for (i = 0; i < num; i++) {
		__be16 *nsrcs, _nsrcs;

		nsrcs = skb_header_pointer(skb,
					   len + offsetof(struct mld2_grec,
							  grec_nsrcs),
					   sizeof(_nsrcs), &_nsrcs);
		if (!nsrcs)
			return -EINVAL;

		if (!pskb_may_pull(skb,
				   len + sizeof(*grec) +
				   sizeof(struct in6_addr) * ntohs(*nsrcs)))
			return -EINVAL;

		grec = (struct mld2_grec *)(skb->data + len);
		len += sizeof(*grec) +
		       sizeof(struct in6_addr) * ntohs(*nsrcs);

		/* We treat these as MLDv1 reports for now. */
		switch (grec->grec_type) {
		case MLD2_MODE_IS_INCLUDE:
		case MLD2_MODE_IS_EXCLUDE:
		case MLD2_CHANGE_TO_INCLUDE:
		case MLD2_CHANGE_TO_EXCLUDE:
		case MLD2_ALLOW_NEW_SOURCES:
		case MLD2_BLOCK_OLD_SOURCES:
			break;

		default:
			continue;
		}

		err = br_ip6_multicast_add_group(br, port, &grec->grec_mca,
						 vid);
		if (!err)
			break;
	}

	return err;
}
