[PATCH 3.4 111/146] x86/mce: Fix MCE severity messages

[lizf]

From: Borislav Petkov <bp@xxxxxxx>

3.4.109-rc1 review patch.  If anyone has any objections, please let me know.

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


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@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1431936437-25286-3-git-send-email-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
---
 arch/x86/kernel/cpu/mcheck/mce.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 0d2db0e..9eeaed4 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -652,11 +652,14 @@ EXPORT_SYMBOL_GPL(machine_check_poll);
 static int mce_no_way_out(struct mce *m, char **msg)
 {
 	int i;
+	char *tmp;
 
 	for (i = 0; i < banks; i++) {
 		m->status = mce_rdmsrl(MSR_IA32_MCx_STATUS(i));
-		if (mce_severity(m, tolerant, msg) >= MCE_PANIC_SEVERITY)
+		if (mce_severity(m, tolerant, &tmp) >= MCE_PANIC_SEVERITY) {
+			*msg = tmp;
 			return 1;
+		}
 	}
 	return 0;
 }
-- 
1.9.1

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