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Message-ID: <201906271029.584EC8319@keescook>
Date: Thu, 27 Jun 2019 10:30:01 -0700
From: Kees Cook <keescook@...omium.org>
To: Andy Lutomirski <luto@...nel.org>
Cc: x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
Florian Weimer <fweimer@...hat.com>, Jann Horn <jannh@...gle.com>,
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 v2 6/8] x86/vsyscall: Change the default vsyscall mode to
xonly
On Wed, Jun 26, 2019 at 09:45:07PM -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.
>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
I still think it'd be valuable to describe any known esoteric cases
here, but regardless:
Reviewed-by: Kees Cook <keescook@...omium.org>
-Kees
> ---
> arch/x86/Kconfig | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 0182d2c67590..32028edc1b0e 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2285,7 +2285,7 @@ config COMPAT_VDSO
> choice
> prompt "vsyscall table for legacy applications"
> depends on X86_64
> - default LEGACY_VSYSCALL_EMULATE
> + default LEGACY_VSYSCALL_XONLY
> help
> Legacy user code that does not know how to find the vDSO expects
> to be able to issue three syscalls by calling fixed addresses in
> --
> 2.21.0
>
--
Kees Cook
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