linux-kernel - Re: [PATCH] virtio_balloon: prevent pfn array overflow

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Date:   Thu, 6 Feb 2020 09:29:27 +0100
From:   David Hildenbrand <david@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org
Cc:     Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org, linux-mm@...ck.org
Subject: Re: [PATCH] virtio_balloon: prevent pfn array overflow

On 06.02.20 08:47, Michael S. Tsirkin wrote:
> Make sure, at build time, that pfn array is big enough to hold a single
> page.  It happens to be true since the PAGE_SHIFT value at the moment is
> 20, which is 1M - exactly 256 4K balloon pages.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>  drivers/virtio/virtio_balloon.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 8e400ece9273..2457c54b6185 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -158,6 +158,8 @@ static void set_page_pfns(struct virtio_balloon *vb,
>  {
>  	unsigned int i;
>  
> +	BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
> +
>  	/*
>  	 * Set balloon pfns pointing at this page.
>  	 * Note that the first pfn points at start of the page.
> 

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

-- 
Thanks,

David / dhildenb