linux-kernel - [PATCH v3 0/3] virtio-mem: disallow mapping virtio-mem memory via /dev/mem

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Message-Id: <20210831202141.13846-1-david@redhat.com>
Date:   Tue, 31 Aug 2021 22:21:38 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     David Hildenbrand <david@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        virtualization@...ts.linux-foundation.org, linux-mm@...ck.org
Subject: [PATCH v3 0/3] virtio-mem: disallow mapping virtio-mem memory via /dev/mem

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.

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 <arnd@...db.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Jason Wang <jasowang@...hat.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Hanjun Guo <guohanjun@...wei.com>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: virtualization@...ts.linux-foundation.org
Cc: linux-mm@...ck.org

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
-- 
2.31.1