4.4-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner tglx@linutronix.de
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 @@ -1031,7 +1031,7 @@ 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 @@ -92,6 +92,7 @@ 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 @@ -1672,6 +1672,11 @@ 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: