From: Greg KH <gregkh@linuxfoundation.org>
To: speck@linutronix.de
Subject: [MODERATED] Re: LVI
Date: Tue, 19 Nov 2019 19:46:26 +0100 [thread overview]
Message-ID: <20191119184626.GA2326631@kroah.com> (raw)
In-Reply-To: <20191119182120.w4pjlvkjncqmv7ln@treble>
On Tue, Nov 19, 2019 at 12:21:20PM -0600, speck for Josh Poimboeuf wrote:
> On Tue, Nov 19, 2019 at 07:12:57PM +0100, speck for Greg KH wrote:
> > > --- a/arch/x86/include/asm/uaccess.h
> > > +++ b/arch/x86/include/asm/uaccess.h
> > > @@ -119,9 +119,9 @@ extern int __get_user_bad(void);
> > >
> > > #define __uaccess_begin() stac()
> > > #define __uaccess_end() clac()
> > > -#define __uaccess_begin_nospec() \
> > > +#define __uaccess_end_nospec() \
> > > ({ \
> > > - stac(); \
> > > + clac(); \
> > > barrier_nospec(); \
> > > })
> >
> > Um, don't we _really_ want stac() here? That's the only thing that is
> > saving our butts in a number of places. Why get rid of it? Otherwise
> > it should be easy to cause a speculatave load by userspace for any
> > address they feel like.
> >
> > Or am I mistaken about what you are trying to solve here?
>
> Notice I renamed it to from __uaccess_begin_nospec() to
> __uaccess_end_nospec() ;-)
>
> The idea is to move the LFENCE from _before_ the copy to _after_ the
> copy. I didn't mess with stac/clac.
Ah, ick, sorry, totally mis-read that thing. Nevermind...
greg k-h
next prev parent reply other threads:[~2019-11-19 18:46 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-19 17:40 [MODERATED] LVI Josh Poimboeuf
2019-11-19 17:51 ` [MODERATED] LVI Andrew Cooper
2019-11-19 18:27 ` Josh Poimboeuf
2019-11-19 19:26 ` Andrew Cooper
2019-11-20 9:52 ` Paolo Bonzini
2019-11-19 18:12 ` Greg KH
2019-11-19 18:21 ` Josh Poimboeuf
2019-11-19 18:46 ` Greg KH [this message]
2019-11-19 18:21 ` Paolo Bonzini
2019-11-19 18:22 ` Andrew Cooper
2019-11-19 18:27 ` Josh Poimboeuf
2019-11-19 18:36 ` Luck, Tony
2019-11-20 17:02 ` Greg KH
2019-11-19 18:39 ` Andrew Cooper
2019-11-19 21:00 ` Josh Poimboeuf
2019-11-19 21:03 ` Josh Poimboeuf
2019-11-20 14:11 ` Andrew Cooper
2019-11-20 8:04 ` Peter Zijlstra
2019-11-20 9:49 ` Andrew Cooper
2019-11-20 17:13 ` Josh Poimboeuf
2019-11-20 17:25 ` Greg KH
2019-11-20 17:29 ` Tyler Hicks
2019-11-20 17:30 ` Andrew Cooper
2019-11-20 17:46 ` Greg KH
2019-11-20 19:09 ` Peter Zijlstra
2019-11-20 19:19 ` Greg KH
2019-11-21 0:50 ` LVI Thomas Gleixner
2019-11-21 13:45 ` [MODERATED] LVI Greg KH
2019-11-26 0:54 ` Andi Kleen
2019-11-26 10:37 ` Greg KH
2019-11-26 18:23 ` Andi Kleen
2019-11-27 7:38 ` Greg KH
2019-11-26 10:55 ` Paolo Bonzini
2019-11-26 18:28 ` Andi Kleen
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