On Fri, Jan 5, 2018 at 6:52 PM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, Jan 5, 2018 at 5:10 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: >> From: Andi Kleen <ak@xxxxxxxxxxxxxxx> >> >> 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. Oh, bother, yes, good catch. It's been a long week. I'll take a look at moving this to uaccess_begin().
