Messages in this thread | | | From | Andy Lutomirski <> | Date | Thu, 1 May 2014 14:39:20 -0700 | Subject | Re: [PATCH 4/7] x86: Add support for rd/wr fs/gs base |
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On Thu, May 1, 2014 at 2:15 PM, Andi Kleen <andi@firstfloor.org> wrote: >> If usergs == kernelgs, then ebx will always be 1 and we'll never end >> up in paranoid_userspace. > > You may miss a reschedule in this obscure case. It shouldn't really > happen because loading a kernel pointer is not useful for user space. > > Doesn't seem like a real issue to me. > > We only happen need to handle it to avoid crashing.
Allowing userspace to prevent itself from being rescheduled by loading something strange into gsbase seems unfortunate.
--Andy
> >> Alternatively, what if the paranoid entry checked whether we're coming >> from userspace at the very beginning and, if so, just jumped to the >> non-paranoid entry? > > That would work, but I doubt it would be worth it. >
> -Andi
-- Andy Lutomirski AMA Capital Management, LLC
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