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SubjectRe: [PATCH v4 10/10] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule
On Tue, 31 May 2011, Andi Kleen wrote:
> > +What: CONFIG_UNSAFE_VSYSCALLS (x86_64)
> > +When: When glibc 2.14 or newer is ubitquitous. Perhaps mid-2012.
> > +Why: Having user-executable code at a fixed address is a security problem.
> > + Turning off CONFIG_UNSAFE_VSYSCALLS mostly removes the risk but will
> > + make the time() function slower on glibc versions 2.13 and below.
>
> I disagree with this description (and the whole idea really)
>
> First it's time+gettimeofday+vgetcu, not just time.
>
> A more accurate description is
>
> "will make all x86-64 Linux programs written to the original pre
> vDSO syscall ABI significantly slower"
>
> And the assumption that all world is using glibc is still as bad
> as it was on the first po.st
>
> And it's still a bad idea. Especially since there's a much better
> alternative anyways for the "security problem" which has none of
> these drawbacks.

How about posting an alternative patch?

Thanks,

tglx


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