linux-kernel - [PATCH v2 6/8] x86/vsyscall: Change the default vsyscall mode to xonly

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Message-Id: <30539f8072d2376b9c9efcc07e6ed0d6bf20e882.1561610354.git.luto@kernel.org>
Date:   Wed, 26 Jun 2019 21:45:07 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Florian Weimer <fweimer@...hat.com>,
        Jann Horn <jannh@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2 6/8] x86/vsyscall: Change the default vsyscall mode to xonly

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>
---
 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