Messages in this thread | | | Date | Thu, 4 Jan 2018 12:49:17 +0100 | From | Pavel Machek <> | Subject | Re: Avoid speculative indirect calls in kernel |
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Hi!
> This is a fix for Variant 2 in > https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html > > Any speculative indirect calls in the kernel can be tricked > to execute any kernel code, which may allow side channel > attacks that can leak arbitrary kernel data.
Ok.
> So we want to avoid speculative indirect calls in the kernel. > > There's a special code sequence called a retpoline that can > do indirect calls without speculation. We use a new compiler > option -mindirect-branch=thunk-extern (gcc patch will be released > separately) to recompile the kernel with this new sequence.
So... this "retpoline" code is quite tricky; I guess it does the right on recent Intel CPUs. Does it also do the right thing on all the AMD, Cyrix, ... variants?
Is it neccessary on all the CPUs? I guess 486 does not need this?
Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html [unhandled content-type:application/pgp-signature] | |