linux-kernel - [PATCH v1 2/3] virtio-mem: disallow mapping virtio-mem memory via /dev/mem

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Date:   Wed, 11 Aug 2021 22:36:11 +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 <andriy.shevchenko@...ux.intel.com>,
        virtualization@...ts.linux-foundation.org, linux-mm@...ck.org
Subject: [PATCH v1 2/3] virtio-mem: disallow mapping virtio-mem memory via /dev/mem

By creating our parent IORESOURCE_SYSTEM_RAM resource with
IORESOURCE_EXCLUSIVE, we will disallow any /dev/mem access to our
device-managed region.

Note that access to the region would still be possible if someone simply
doesn't load the virtio-mem driver; however, there is no way of
protecting against someone that just wants to do nasty things.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 drivers/virtio/virtio_mem.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 09ed55de07d7..c8f914700a42 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -2516,8 +2516,10 @@ static int virtio_mem_create_resource(struct virtio_mem *vm)
 	if (!name)
 		return -ENOMEM;
 
+	/* Disallow mapping device memory via /dev/mem completely. */
 	vm->parent_resource = __request_mem_region(vm->addr, vm->region_size,
-						   name, IORESOURCE_SYSTEM_RAM);
+						   name, IORESOURCE_SYSTEM_RAM |
+						   IORESOURCE_EXCLUSIVE);
 	if (!vm->parent_resource) {
 		kfree(name);
 		dev_warn(&vm->vdev->dev, "could not reserve device region\n");
-- 
2.31.1