[PATCH 4.14 19/31] x86/MCE/AMD: Always give panic severity for UC errors in kernel context

From: Greg Kroah-Hartman
Date: Sun Nov 19 2017 - 10:00:46 EST

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


From: Yazen Ghannam <yazen.ghannam@xxxxxxx>

commit d65dfc81bb3894fdb68cbc74bbf5fb48d2354071 upstream.

The AMD severity grading function was introduced in kernel 4.1. The
current logic can possibly give MCE_AR_SEVERITY for uncorrectable
errors in kernel context. The system may then get stuck in a loop as
memory_failure() will try to handle the bad kernel memory and find it

Return MCE_PANIC_SEVERITY for all UC errors IN_KERNEL context on AMD


b2f9d678e28c ("x86/mce: Check for faults tagged in EXTABLE_CLASS_FAULT exception table entries")

was accepted in v4.6, this issue was masked because of the tail-end attempt
at kernel mode recovery in the #MC handler.

However, uncorrectable errors IN_KERNEL context should always be considered
unrecoverable and cause a panic.

Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: linux-edac <linux-edac@xxxxxxxxxxxxxxx>
Fixes: bf80bbd7dcf5 (x86/mce: Add an AMD severities-grading function)
Link: http://lkml.kernel.org/r/20171106174633.13576-1-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/x86/kernel/cpu/mcheck/mce-severity.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

--- a/arch/x86/kernel/cpu/mcheck/mce-severity.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c
@@ -245,6 +245,9 @@ static int mce_severity_amd(struct mce *

if (m->status & MCI_STATUS_UC) {

+ if (ctx == IN_KERNEL)
* On older systems where overflow_recov flag is not present, we
* should simply panic if an error overflow occurs. If
@@ -255,10 +258,6 @@ static int mce_severity_amd(struct mce *
if (mce_flags.smca)
return mce_severity_amd_smca(m, ctx);

- /* software can try to contain */
- if (!(m->mcgstatus & MCG_STATUS_RIPV) && (ctx == IN_KERNEL))
/* kill current process */
} else {