Validate sender credentials on netlink msg receive

Verify that netlink messages are actually from the kernel,
and not from a userspace program.

This is a manual cherry-pick from b620a0b1c7ae486e979826200e8e441605b0a5d6

Change-Id: I237f0a5cb56393bb3aab64a7ae5898f2bdc95cef
1 file changed