From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 18 Jan 2018 16:28:26 +0100
Subject: x86/mce: Make machine check speculation protected
Git-commit: 6f41c34d69eb005e7848716bbcafc979b35037d5
Patch-mainline: v4.15-rc9
References: bsc#1068032 CVE-2017-5754
The machine check idtentry uses an indirect branch directly from the low
level code. This evades the speculation protection.
Replace it by a direct call into C code and issue the indirect call there
so the compiler can apply the proper speculation protection.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by:Borislav Petkov <bp@alien8.de>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Niced-by: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801181626290.1847@nanos
Acked-by: Borislav Petkov <bp@suse.de>
---
arch/x86/entry/entry_64.S | 2 +-
arch/x86/include/asm/traps.h | 1 +
arch/x86/kernel/cpu/mcheck/mce.c | 5 +++++
3 files changed, 7 insertions(+), 1 deletion(-)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1281,7 +1281,7 @@ idtentry async_page_fault do_async_page_
#endif
#ifdef CONFIG_X86_MCE
-idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip)
+idtentry machine_check do_mce has_error_code=0 paranoid=1
#endif
/*
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -113,6 +113,7 @@ dotraplinkage void do_simd_coprocessor_e
#ifdef CONFIG_X86_32
dotraplinkage void do_iret_error(struct pt_regs *, long);
#endif
+dotraplinkage void do_mce(struct pt_regs *, long);
static inline int get_si_code(unsigned long condition)
{
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1750,6 +1750,11 @@ static void unexpected_machine_check(str
void (*machine_check_vector)(struct pt_regs *, long error_code) =
unexpected_machine_check;
+dotraplinkage void do_mce(struct pt_regs *regs, long error_code)
+{
+ machine_check_vector(regs, error_code);
+}
+
/*
* Called for each booted CPU to set up machine checks.
* Must be called with preempt off: