linux-kernel - [PATCH 2/2] x86/mce: Use only critical MCE severity message

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Date:	Mon, 18 May 2015 10:07:17 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/2] x86/mce: Use only critical MCE severity message

From: Borislav Petkov <bp@...e.de>

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

  [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
  				   ^^^^^^^

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@...il.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Tony Luck <tony.luck@...el.com>
Cc: <stable@...r.kernel.org>
---
 arch/x86/kernel/cpu/mcheck/mce.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 521e5016aca6..4d450ac74e3d 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -708,6 +708,7 @@ 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));
@@ -716,9 +717,11 @@ 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, true) >=
-		    MCE_PANIC_SEVERITY)
+
+		if (mce_severity(m, mca_cfg.tolerant, &tmp, true) >= MCE_PANIC_SEVERITY) {
+			*msg = tmp;
 			ret = 1;
+		}
 	}
 	return ret;
 }
-- 
2.3.5

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