linux-kernel - [PATCH v2 7/8] x86/vsyscall: Add __ro_after

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Message-Id: <a386925835e49d319e70c4d7404b1f6c3c2e3702.1561610354.git.luto@kernel.org>
Date:   Wed, 26 Jun 2019 21:45:08 -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 7/8] x86/vsyscall: Add __ro_after_init to global variables

The vDSO is only configurable by command-line options, so make its
global variables __ro_after_init.  This seems highly unlikely to
ever stop an exploit, but I think it's nice anyway.

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/entry/vsyscall/vsyscall_64.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 9c58ab807aeb..07003f3f1bfc 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -42,7 +42,7 @@
 #define CREATE_TRACE_POINTS
 #include "vsyscall_trace.h"
 
-static enum { EMULATE, XONLY, NONE } vsyscall_mode =
+static enum { EMULATE, XONLY, NONE } vsyscall_mode __ro_after_init =
 #ifdef CONFIG_LEGACY_VSYSCALL_NONE
 	NONE;
 #elif defined(CONFIG_LEGACY_VSYSCALL_XONLY)
@@ -305,7 +305,7 @@ static const char *gate_vma_name(struct vm_area_struct *vma)
 static const struct vm_operations_struct gate_vma_ops = {
 	.name = gate_vma_name,
 };
-static struct vm_area_struct gate_vma = {
+static struct vm_area_struct gate_vma __ro_after_init = {
 	.vm_start	= VSYSCALL_ADDR,
 	.vm_end		= VSYSCALL_ADDR + PAGE_SIZE,
 	.vm_page_prot	= PAGE_READONLY_EXEC,
-- 
2.21.0