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Subject: Re: [PATCH v2 0/3] virtio-mem: disallow mapping virtio-mem memory via
 /dev/mem
To:     linux-kernel@vger.kernel.org
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Hanjun Guo <guohanjun@huawei.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        virtualization@lists.linux-foundation.org, linux-mm@kvack.org
References: <20210816142505.28359-1-david@redhat.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
Message-ID: <aa136104-153c-1c85-54df-f55b953ff36d@redhat.com>
Date:   Mon, 23 Aug 2021 21:14:59 +0200
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On 16.08.21 16:25, David Hildenbrand wrote:
> 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@arndb.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Hanjun Guo <guohanjun@huawei.com>
> Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
> Cc: virtualization@lists.linux-foundation.org
> Cc: linux-mm@kvack.org
> 
> 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
> 

More review welcome; I'd suggest this should go via the -mm tree, and 
not via the vhost tree.

-- 
Thanks,

David / dhildenb