PCI: Lock down BAR access when the kernel is locked down

PCI: Lock down BAR access when the kernel is locked down

Any hardware that can potentially generate DMA has to be locked down in
order to avoid it being possible for an attacker to modify kernel code,
allowing them to circumvent disabled module loading or module signing.
Default to paranoid - in future we can potentially relax this for
sufficiently IOMMU-isolated devices.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
[bwh: For 4.12, adjust context]

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0049-PCI-Lock-down-BAR-access-when-the-kernel-is-locked-d.patch