From: Yazen Ghannam yazen.ghannam@amd.com

[Upstream commit d65dfc81bb3894fdb68cbc74bbf5fb48d2354071]

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 Cc: stable@vger.kernel.org # 4.1.x, 4.4.x Fixes: bf80bbd7dcf5 (x86/mce: Add an AMD severities-grading function) --- Same as d65dfc81bb38 ("x86/MCE/AMD: Always give panic severity for UC errors in kernel context") but fixed up to apply to v4.1 and v4.4 stable branches.

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

diff --git a/arch/x86/kernel/cpu/mcheck/mce-severity.c b/arch/x86/kernel/cpu/mcheck/mce-severity.c index 9c682c222071..a9287f0f06f2 100644 --- a/arch/x86/kernel/cpu/mcheck/mce-severity.c +++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c @@ -200,6 +200,9 @@ static int mce_severity_amd(struct mce *m, int tolerant, char **msg, bool is_exc

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 @@ -207,10 +210,6 @@ static int mce_severity_amd(struct mce *m, int tolerant, char **msg, bool is_exc * to at least kill process to prolong system operation. */ if (mce_flags.overflow_recov) { - /* 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 {