[v4,0/3] virtio-mem: disallow mapping virtio-mem memory via /dev/mem

Message

David Hildenbrand Sept. 2, 2021, 4:09 p.m. UTC

I think this might be a good fit for the -mm tree, as the actual virtio-mem
changes are rather small.

--

Let's add the basic infrastructure to exclude some physical memory
regions marked as "IORESOURCE_SYSTEM_RAM" completely from /dev/mem access,
even though they are not marked IORESOURCE_BUSY and even though
"iomem=relaxed" is set. Resource IORESOURCE_EXCLUSIVE for that purpose
instead of adding new flags to express something similar to
"soft-busy" or "not busy yet, but already prepared by a driver and not
to be mapped by user space".

Use it for virtio-mem, to disallow mapping any virtio-mem memory via
/dev/mem to user space after the virtio-mem driver was loaded.

Details can be found in patch #2 and #3.

v3 -> v4:
- Added Dans RBs (thanks!)
- Actually send the patches to the CC list ...

v2 -> v3:
- "kernel/resource: clean up and optimize iomem_is_exclusive()"
-- Reshuffled and moved for_each_resource() etc. into this patch
- "kernel/resource: disallow access to exclusive system RAM regions"
-- Leave CONFIG_STRICT_DEVMEM=n alone. Hoog into iomem_is_exclusive()
   instead.
-- Improve comments
- "virtio-mem: disallow mapping virtio-mem memory via /dev/mem"
-- Don't allow building virtio_mem without CONFIG_STRICT_DEVMEM when we
   have CONFIG_DEVMEM, where we don't have any guarantees.
- Rework all patch descriptions

v1 -> v2:
- "/dev/mem: disallow access to explicitly excluded system RAM regions"
-- Introduce and use for_each_resource() and next_resource_skip_children()
-- s/iomem_range_contains_excluded/iomem_range_contains_excluded_devmem/
- "kernel/resource: cleanup and optimize iomem_is_exclusive()"
-- Use for_each_resource()

Cc: Arnd Bergmann <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: "Michael S. Tsirkin" <[e-mail]>
Cc: Jason Wang <[e-mail]>
Cc: "Rafael J. Wysocki" <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Hanjun Guo <[e-mail]>
Cc: Andy Shevchenko <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]

David Hildenbrand (3):
  kernel/resource: clean up and optimize iomem_is_exclusive()
  kernel/resource: disallow access to exclusive system RAM regions
  virtio-mem: disallow mapping virtio-mem memory via /dev/mem

 drivers/virtio/Kconfig      |  1 +
 drivers/virtio/virtio_mem.c |  4 ++-
 kernel/resource.c           | 54 ++++++++++++++++++++++++++-----------
 3 files changed, 43 insertions(+), 16 deletions(-)


base-commit: 7d2a07b769330c34b4deabeed939325c77a7ec2f