[patch V149 03/50] x86/vsyscall/64: Warn and fail vsyscall emulation in NATIVE mode

From: Thomas Gleixner
Date: Sat Dec 16 2017 - 16:48:33 EST

From: Andy Lutomirski <luto@xxxxxxxxxx>

If something goes wrong with pagetable setup, vsyscall=native will
accidentally fall back to emulation. Make it warn and fail so that we

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
arch/x86/entry/vsyscall/vsyscall_64.c | 4 ++++
1 file changed, 4 insertions(+)

Index: tip/arch/x86/entry/vsyscall/vsyscall_64.c
--- tip.orig/arch/x86/entry/vsyscall/vsyscall_64.c
+++ tip/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -138,6 +138,10 @@ bool emulate_vsyscall(struct pt_regs *re

WARN_ON_ONCE(address != regs->ip);

+ /* This should be unreachable in NATIVE mode. */
+ if (WARN_ON(vsyscall_mode == NATIVE))
+ return false;
if (vsyscall_mode == NONE) {
warn_bad_vsyscall(KERN_INFO, regs,
"vsyscall attempted with vsyscall=none");