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

x86/MCE/AMD: Always give panic severity for UC errors in kernel context

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-mce-amd-always-give-panic-severity-for-uc-errors-in-kernel-context.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From d65dfc81bb3894fdb68cbc74bbf5fb48d2354071 Mon Sep 17 00:00:00 2001

From: Yazen Ghannam yazen.ghannam@amd.com Date: Mon, 6 Nov 2017 18:46:32 +0100 Subject: x86/MCE/AMD: Always give panic severity for UC errors in kernel context

From: Yazen Ghannam yazen.ghannam@amd.com

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 busy.

Return MCE_PANIC_SEVERITY for all UC errors IN_KERNEL context on AMD systems.

After:

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@amd.com Signed-off-by: Borislav Petkov bp@suse.de Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Tony Luck tony.luck@intel.com Cc: linux-edac linux-edac@vger.kernel.org Fixes: bf80bbd7dcf5 (x86/mce: Add an AMD severities-grading function) Link: http://lkml.kernel.org/r/20171106174633.13576-1-bp@alien8.de Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- 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) + return MCE_PANIC_SEVERITY; + /* * 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)) - return MCE_PANIC_SEVERITY; - /* kill current process */ return MCE_AR_SEVERITY; } else {

Patches currently in stable-queue which might be from yazen.ghannam@amd.com are

queue-4.14/x86-mce-amd-always-give-panic-severity-for-uc-errors-in-kernel-context.patch