Re: [Xen-devel] [PATCH v5 09/10] xen/arm: Set foreign page type to p2m_map_foreign

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-12-16 at 17:37 +0000, Julien Grall wrote:
> Xen needs to know that the current page belongs to another domain. Also take
> a reference to this page.
> 
> The current process to add a foreign page is:
>    1) get the page from the foreign p2m
>    2) take a reference on the page with the foreign domain in parameters
>    3) add the page to the current domain p2m
> 
> If the foreign domain drops the page:
>     - before 2), get_page will return NULL because the page doesn't
>     belong anymore to the domain
>     - after 2), the current domain already have a reference. Write will
>     occur to an old page which is not yet released. It can corrupt the foreign
>     domain.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

Ian.


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