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xen-devel
Re: [Xen-devel] Is exposing shared_info to user-land secure?
Dan Magenheimer wrote:
Is it "safe" in a paravirtualized guest to expose shared_info
(at least read-only) to user-land? That is, is there data
in shared_info that could be used by a malicious program to
compromise a guest OS (ignoring very complex side-channel
attacks anyway)?
We have apps that constantly do various time syscalls (e.g.
to gettimeofday()) and I'm thinking if vcpu_info(cpu)->time_info
was directly readable by an enterprise app, it could do
the time calculations itself and save the syscall overhead.
You can use the HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, )
hypercall to move the vcpu structure out of the shared info structure;
that could be placed somewhere mappable. Though currently I use it to
put it into the percpu data area for quick kernel access; it definitely
wouldn't be mappable by userspace there (well, not without padding it
out to its own page, at least).
J
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