ipv6: Fix the size overflow of addrconf_sysctl array

(This patch fixes bug of commit f7734fdf
 title "make TLLAO option for NA packets configurable")

When the IPV6 conf is used, the function sysctl_set_parent is called and the
array addrconf_sysctl is used as a parameter of the function.

The above patch added new conf "force_tllao" into the array addrconf_sysctl,
but the size of the array was not modified, the static allocated size is
DEVCONF_MAX + 1 but the real size is DEVCONF_MAX + 2, so the problem is
that the function sysctl_set_parent accessed wrong address.

I got the following information.
Call Trace:
    [<ffffffff8106085d>] sysctl_set_parent+0x29/0x3e
    [<ffffffff8106085d>] sysctl_set_parent+0x29/0x3e
    [<ffffffff8106085d>] sysctl_set_parent+0x29/0x3e
    [<ffffffff8106085d>] sysctl_set_parent+0x29/0x3e
    [<ffffffff8106085d>] sysctl_set_parent+0x29/0x3e
    [<ffffffff810622d5>] __register_sysctl_paths+0xde/0x272
    [<ffffffff8110892d>] ? __kmalloc_track_caller+0x16e/0x180
    [<ffffffffa00cfac3>] ? __addrconf_sysctl_register+0xc5/0x144 [ipv6]
    [<ffffffff8141f2c9>] register_net_sysctl_table+0x48/0x4b
    [<ffffffffa00cfaf5>] __addrconf_sysctl_register+0xf7/0x144 [ipv6]
    [<ffffffffa00cfc16>] addrconf_init_net+0xd4/0x104 [ipv6]
    [<ffffffff8139195f>] setup_net+0x35/0x82
    [<ffffffff81391f6c>] copy_net_ns+0x76/0xe0
    [<ffffffff8107ad60>] create_new_namespaces+0xf0/0x16e
    [<ffffffff8107afee>] copy_namespaces+0x65/0x9f
    [<ffffffff81056dff>] copy_process+0xb2c/0x12c3
    [<ffffffff810576e1>] do_fork+0x14b/0x2d2
    [<ffffffff8107ac4e>] ? up_read+0xe/0x10
    [<ffffffff81438e73>] ? do_page_fault+0x27a/0x2aa
    [<ffffffff8101044b>] sys_clone+0x28/0x2a
    [<ffffffff81011fb3>] stub_clone+0x13/0x20
    [<ffffffff81011c72>] ? system_call_fastpath+0x16/0x1b

And the information of IPV6 in .config is as following.
IPV6 in .config:
    CONFIG_IPV6=m
    CONFIG_IPV6_PRIVACY=y
    CONFIG_IPV6_ROUTER_PREF=y
    CONFIG_IPV6_ROUTE_INFO=y
    CONFIG_IPV6_OPTIMISTIC_DAD=y
    CONFIG_IPV6_MIP6=m
    CONFIG_IPV6_SIT=m
    # CONFIG_IPV6_SIT_6RD is not set
    CONFIG_IPV6_NDISC_NODETYPE=y
    CONFIG_IPV6_TUNNEL=m
    CONFIG_IPV6_MULTIPLE_TABLES=y
    CONFIG_IPV6_SUBTREES=y
    CONFIG_IPV6_MROUTE=y
    CONFIG_IPV6_PIMSM_V2=y
    # CONFIG_IP_VS_IPV6 is not set
    CONFIG_NF_CONNTRACK_IPV6=m
    CONFIG_IP6_NF_MATCH_IPV6HEADER=m

I confirmed this patch fixes this problem.
Signed-off-by: Jin Dongming <jin.dongming@np.css.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -208,6 +208,7 @@ enum {
 	DEVCONF_MC_FORWARDING,
 	DEVCONF_DISABLE_IPV6,
 	DEVCONF_ACCEPT_DAD,
+	DEVCONF_FORCE_TLLAO,
 	DEVCONF_MAX
 };