[lkml]   [2018]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 06/18] x86, barrier: stop speculation for failed access_ok
On Fri, Jan 5, 2018 at 6:52 PM, Linus Torvalds
<> wrote:
> On Fri, Jan 5, 2018 at 5:10 PM, Dan Williams <> wrote:
>> From: Andi Kleen <>
>> 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().

 \ /
  Last update: 2018-01-06 06:47    [W:0.203 / U:5.740 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site