Re: [Xen-devel] [PATCH 00/14] XSA-277 followup

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Wed, Nov 21, 2018 at 6:21 AM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>
> This covers various fixes related to XSA-277 which weren't in security
> supported areas, and associated cleanup.
>
> The biggest issue noticed here is that altp2m's use of hardware #VE support
> will cause general memory corruption if the guest ever balloons out the VEINFO
> page.  The only safe way I think of doing this is for Xen to alloc annonymous
> domheap pages for the VEINFO, and for the guest to map them in a similar way
> to the shared info and grant table frames.

Since ballooning presents all sorts of problems when used with altp2m
I would suggest just making the two explicitly incompatible during
domain creation. Beside the info page being possibly ballooned out the
other problem is when ballooning causes altp2m views to be reset
completely, removing mem_access permissions and remapped entries.

Tamas

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