Patch "x86/mce: Fix MCE severity messages" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

x86/mce: Fix MCE severity messages

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-mce-fix-mce-severity-messages.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Borislav Petkov <[email protected]>
Date: Mon, 18 May 2015 10:07:17 +0200
Subject: x86/mce: Fix MCE severity messages

From: Borislav Petkov <[email protected]>

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.

---
 arch/x86/kernel/cpu/mcheck/mce.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

@@ -705,6 +705,7 @@ static int mce_no_way_out(struct mce *m,
 			  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));

@@ -713,9 +714,11 @@ static int mce_no_way_out(struct mce *m,
 			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;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/x86-mce-fix-mce-severity-messages.patch