linux-kernel - Re: [PATCH AUTOSEL 5.10 3/4] virtio-mem: support VIRTIO_MEM_F_UNPLUGGED

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Date:   Fri, 26 Nov 2021 09:51:09 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Marek Kedzierski <mkedzier@...hat.com>,
        Hui Zhu <teawater@...il.com>,
        Sebastien Boeuf <sebastien.boeuf@...el.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH AUTOSEL 5.10 3/4] virtio-mem: support
 VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE

On 26.11.21 03:30, Sasha Levin wrote:
> From: David Hildenbrand <david@...hat.com>
> 
> [ Upstream commit 61082ad6a6e1f999eef7e7e90046486c87933b1e ]
> 
> The initial virtio-mem spec states that while unplugged memory should not
> be read, the device still has to allow for reading unplugged memory inside
> the usable region. The primary motivation for this default handling was
> to simplify bringup of virtio-mem, because there were corner cases where
> Linux might have accidentially read unplugged memory inside added Linux
> memory blocks.
> 
> In the meantime, we:
> 1. Removed /dev/kmem in commit bbcd53c96071 ("drivers/char: remove
>    /dev/kmem for good")
> 2. Disallowed access to virtio-mem device memory via /dev/mem in
>    commit 2128f4e21aa2 ("virtio-mem: disallow mapping virtio-mem memory via
>    /dev/mem")
> 3. Sanitized access to virtio-mem device memory via /proc/kcore in
>    commit 0daa322b8ff9 ("fs/proc/kcore: don't read offline sections,
>    logically offline pages and hwpoisoned pages")
> 4. Sanitized access to virtio-mem device memory via /proc/vmcore in
>    commit ce2814622e84 ("virtio-mem: kdump mode to sanitize /proc/vmcore
>    access")

As 2. and 4. are part of v5.16-rc1 but not v5.10-stable

Nacked-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb