x86/mce: Make machine check speculation protected

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

3 files changed, 7 insertions, 1 deletions

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index d54a0ede61d1..63f4320602a3 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1258,7 +1258,7 @@ idtentry async_page_fault	do_async_page_fault	has_error_code=1
 #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
 
 /*
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 31051f35cbb7..3de69330e6c5 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -88,6 +88,7 @@ dotraplinkage void do_simd_coprocessor_error(struct pt_regs *, long);
 #ifdef CONFIG_X86_32
 dotraplinkage void do_iret_error(struct pt_regs *, long);
 #endif
+dotraplinkage 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 3b413065c613..a9e898b71208 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1788,6 +1788,11 @@ 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;
 
+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: