Re: [Xen-devel] readonly grants

[Tim Deegan <tim@xxxxxxx>]

At 20:16 +0330 on 26 Oct (1319660209), Mohammad Hedayati wrote:
> After mapping a readonly granted page in a PV guest, the guest can try to
> change his l1 page table entry, faulting into Xen. Here xen emulates the
> update operation, but first it must check whether the modification is
> allowed or not (i.e. the grant is readonly or not).
> I'm looking through the code, but I can't find where this checking is done.

Emulated writes go through ptwr_emulated_update() which calls
get_page_from_l1e(), which won't let the guest write a PTE that maps
another VM's memory.

Tim.

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