[PATCH 3.16.y-ckt 014/185] x86/mce: Fix MCE severity messages

[Luis Henriques]

3.16.7-ckt15 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Borislav Petkov <bp at suse.de>

commit 17fea54bf0ab34fa09a06bbde2f58ed7bbdf9299 upstream.

Derek noticed that a critical MCE gets reported with the wrong
error type description:

  [Hardware Error]: CPU 34: Machine Check Exception: 5 Bank 9: f200003f000100b0
  [Hardware Error]: RIP !INEXACT! 10:<ffffffff812e14c1> {intel_idle+0xb1/0x170}
  [Hardware Error]: TSC 49587b8e321cb
  [Hardware Error]: PROCESSOR 0:306e4 TIME 1431561296 SOCKET 1 APIC 29
  [Hardware Error]: Some CPUs didn't answer in synchronization
  [Hardware Error]: Machine check: Invalid
				   ^^^^^^^

The last line with 'Invalid' should have printed the high level
MCE error type description we get from mce_severity, i.e.
something like:

  [Hardware Error]: Machine check: Action required: data load error in a user process

this happens due to the fact that mce_no_way_out() iterates over
all MCA banks and possibly overwrites the @msg argument which is
used in the panic printing later.

Change behavior to take the message of only and the (last)
critical MCE it detects.

Reported-by: Derek <denc716 at gmail.com>
Signed-off-by: Borislav Petkov <bp at suse.de>
Cc: H. Peter Anvin <hpa at zytor.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Tony Luck <tony.luck at intel.com>
Link: http://lkml.kernel.org/r/1431936437-25286-3-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo at kernel.org>
[ kamal: backport to 3.13-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/x86/kernel/cpu/mcheck/mce.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 9a79c8dbd8e8..5648b506f3ae 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -660,6 +660,7 @@ static int mce_no_way_out(struct mce *m, char **msg, unsigned long *validp,
 			  struct pt_regs *regs)
 {
 	int i, ret = 0;
+	char *tmp;
 
 	for (i = 0; i < mca_cfg.banks; i++) {
 		m->status = mce_rdmsrl(MSR_IA32_MCx_STATUS(i));
@@ -668,8 +669,11 @@ static int mce_no_way_out(struct mce *m, char **msg, unsigned long *validp,
 			if (quirk_no_way_out)
 				quirk_no_way_out(i, m, regs);
 		}
-		if (mce_severity(m, mca_cfg.tolerant, msg) >= MCE_PANIC_SEVERITY)
+
+		if (mce_severity(m, mca_cfg.tolerant, &tmp) >= MCE_PANIC_SEVERITY) {
+			*msg = tmp;
 			ret = 1;
+		}
 	}
 	return ret;
 }