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 c02db8c6290b ("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: c02db8c6290b ("rtnetlink: make SR-IOV VF interface symmetric")
Reported-by: Jason Gunthorpe <[email protected]>
Cc: Chris Wright <[email protected]>
Cc: Sucheta Chakraborty <[email protected]>
Cc: Greg Rose <[email protected]>
Cc: Jeff Kirsher <[email protected]>
Cc: Rony Efraim <[email protected]>
Cc: Vlad Zolotarov <[email protected]>
Cc: Nicolas Dichtel <[email protected]>
Cc: Thomas Graf <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Vlad Zolotarov <[email protected]>
Signed-off-by: David S. Miller <[email protected]>