addrconf: always initialize sysctl table data

addrconf: always initialize sysctl table data

Orabug: 23330541

[ Upstream commit 5449a5ca9bc27dd51a462de7ca0b1cd861cd2bd0 ]

When sysctl performs restrict writes, it allows to write from
a middle position of a sysctl file, which requires us to initialize
the table data before calling proc_dostring() for the write case.

Fixes: 3d1bec99320d ("ipv6: introduce secret_stable to ipv6_devconf")
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 6866b52c56db189f8471a13f951221c45c0089c7)

Signed-off-by: Dan Duval <dan.duval@oracle.com>