[PATCH v2 0/3] virtio-mem: disallow mapping virtio-mem memory via /dev/mem

From: David Hildenbrand
Date: Mon Aug 16 2021 - 10:25:25 EST


Let's add the basic infrastructure to exclude some physical memory
regions completely from /dev/mem access, on any architecture and under
any system configuration (independent of CONFIG_STRICT_DEVMEM and
independent of "iomem=").

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: there is
no sane use case to access the device-managed memory region via /dev/mem
once the driver is actively (un)plugging memory within that region and
we want to make sure that nobody will accidentially access unplugged
memory in a sane environment.

Details can be found in patch #1.

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 <arnd@xxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Hanjun Guo <guohanjun@xxxxxxxxxx>
Cc: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx

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

drivers/char/mem.c | 22 ++++++--------
drivers/virtio/virtio_mem.c | 4 ++-
include/linux/ioport.h | 1 +
kernel/resource.c | 60 +++++++++++++++++++++++++++++++++----
lib/Kconfig.debug | 4 ++-
5 files changed, 71 insertions(+), 20 deletions(-)


base-commit: 7c60610d476766e128cc4284bb6349732cbd6606
--
2.31.1