| From | Linus Torvalds <> | Date | Fri, 5 Jan 2018 18:52:07 -0800 | Subject | Re: [PATCH 06/18] x86, barrier: stop speculation for failed access_ok |
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On Fri, Jan 5, 2018 at 5:10 PM, Dan Williams <dan.j.williams@intel.com> wrote: > From: Andi Kleen <ak@linux.intel.com> > > When access_ok fails we should always stop speculating. > Add the required barriers to the x86 access_ok macro.
Honestly, this seems completely bogus.
The description is pure garbage afaik.
The fact is, we have to stop speculating when access_ok() does *not* fail - because that's when we'll actually do the access. And it's that access that needs to be non-speculative.
That actually seems to be what the code does (it stops speculation when __range_not_ok() returns false, but access_ok() is !__range_not_ok()). But the explanation is crap, and dangerous.
Linus
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