On Fri, 2018-01-12 at 10:57 -0700, Jeff Law wrote: > > WRT text relocs, yea that sucks, but if we're going to have user space > mitigations, then we're likely going to need those relocs so that the > thunks can be patched out. I'm actually hoping we're not going to need > user space mitigations for spectre v2 and we can avoid this problem..
As things stand with retpoline in the kernel, userspace processes aren't protected from each other. The attack mode is complex and probably fairly unlikely, and we need to get the new microcode support into the kernel, with the IBPB (flush branch predictor) MSR. And for the kernel to use it, of course. In the meantime, it does potentially make sense for sensitive userspace processes to be compiled this way. Especially if they're going to run external code (like JavaScript) and attempt to sandbox it — which is something that IBPB isn't going to solve either.
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