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Message-ID: <CALCETrUYNavL8pu4jQqJjoT=PdeRyjeoLDn=0r7h=2XsHDMezQ@mail.gmail.com>
Date: Thu, 13 Jun 2019 12:14:50 -0700
From: Andy Lutomirski <luto@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
Borislav Petkov <bp@...en8.de>, Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 5/5] x86/vsyscall: Change the default vsyscall mode to xonly
On Mon, Jun 10, 2019 at 1:44 PM Kees Cook <keescook@...omium.org> wrote:
>
> On Mon, Jun 10, 2019 at 01:25:31PM -0700, Andy Lutomirski wrote:
> > The use case for full emulation over xonly is very esoteric. Let's
> > change the default to the safer xonly mode.
>
> Perhaps describe the esoteric cases here (and maybe in the Kconfig help
> text)? That should a user determine if they actually need it. (What
> would the failure under xonly look like for someone needing emulate?)
I added it to the Kconfig text.
Right now, the failure will just be a segfault. I could add some
logic so that it would log "invalid read to vsyscall page -- fix your
userspace or boot with vsyscall=emulate". Do you think that's
important?
--Andy
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