rtnetlink: verify IFLA_VF_INFO attributes before passing them to driver

rtnetlink: verify IFLA_VF_INFO attributes before passing them to driver

Jason Gunthorpe reported that since commit e1c2c45c8124 ("rtnetlink: make
SR-IOV VF interface symmetric"), we don't verify IFLA_VF_INFO attributes
anymore with respect to their policy, that is, ifla_vfinfo_policy[].

Before, they were part of ifla_policy[], but they have been nested since
placed under IFLA_VFINFO_LIST, that contains the attribute IFLA_VF_INFO,
which is another nested attribute for the actual VF attributes such as
IFLA_VF_MAC, IFLA_VF_VLAN, etc.

Despite the policy being split out from ifla_policy[] in this commit,
it's never applied anywhere. nla_for_each_nested() only does basic nla_ok()
testing for struct nlattr, but it doesn't know about the data context and
their requirements.

Fix, on top of Jason's initial work, does 1) parsing of the attributes
with the right policy, and 2) using the resulting parsed attribute table
from 1) instead of the nla_for_each_nested() loop (just like we used to
do when still part of ifla_policy[]).

Reference: http://thread.gmane.org/gmane.linux.network/368913
Fixes: e1c2c45c8124 ("rtnetlink: make SR-IOV VF interface symmetric")
Reported-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Cc: Greg Rose <gregory.v.rose@intel.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: Rony Efraim <ronye@mellanox.com>
Cc: Vlad Zolotarov <vladz@cloudius-systems.com>
Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Cc: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Signed-off-by: David S. Miller <davem@davemloft.net>