From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 18 Jan 2018 15:28:26 +0000 (+0100)
Subject: x86/mce: Make machine check speculation protected
X-Git-Tag: v3.2.100~29
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=24578f5e4c465369b7663873ce7c8bcbc77f7965;p=thirdparty%2Fkernel%2Fstable.git

x86/mce: Make machine check speculation protected

commit 6f41c34d69eb005e7848716bbcafc979b35037d5 upstream.

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>
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801181626290.1847@nanos
[bwh: Backported to 3.2:
 - Don't use dotraplinkage
 - Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 88eae2aec619e..e8666d8be9c41 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -69,6 +69,7 @@ dotraplinkage void do_simd_coprocessor_error(struct pt_regs *, long);
 #ifdef CONFIG_X86_32
 dotraplinkage void do_iret_error(struct pt_regs *, long);
 #endif
+void do_mce(struct pt_regs *, long);
 
 static inline int get_si_code(unsigned long condition)
 {
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 3b678770dba57..fc54c3b3df81a 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1407,6 +1407,11 @@ static void unexpected_machine_check(struct pt_regs *regs, long error_code)
 void (*machine_check_vector)(struct pt_regs *, long error_code) =
 						unexpected_machine_check;
 
+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:
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index b232bfcf44fbd..c13ca52ce42e5 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1399,7 +1399,7 @@ errorentry page_fault do_page_fault
 errorentry async_page_fault do_async_page_fault
 #endif
 #ifdef CONFIG_X86_MCE
-paranoidzeroentry machine_check *machine_check_vector(%rip)
+paranoidzeroentry machine_check do_mce
 #endif
 
 	/*