From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756580AbbFQXWz (ORCPT ); Wed, 17 Jun 2015 19:22:55 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35087 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932786AbbFQW0F (ORCPT ); Wed, 17 Jun 2015 18:26:05 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Mahesh Salgaonkar , Christoph Lameter , Daniel Axtens , Michael Ellerman , Kamal Mostafa Subject: [PATCH 3.19.y-ckt 091/146] powerpc/mce: fix off by one errors in mce event handling Date: Wed, 17 Jun 2015 15:23:16 -0700 Message-Id: <1434579851-1719-92-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1434579851-1719-1-git-send-email-kamal@canonical.com> References: <1434579851-1719-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.19.8-ckt2 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Axtens commit ffb2d78eca08a1451137583d4e435aecfd6af809 upstream. Before 69111bac42f5 ("powerpc: Replace __get_cpu_var uses"), in save_mce_event, index got the value of mce_nest_count, and mce_nest_count was incremented *after* index was set. However, that patch changed the behaviour so that mce_nest count was incremented *before* setting index. This causes an off-by-one error, as get_mce_event sets index as mce_nest_count - 1 before reading mce_event. Thus get_mce_event reads bogus data, causing warnings like "Machine Check Exception, Unknown event version 0 !" and breaking MCEs handling. Restore the old behaviour and unbreak MCE handling by subtracting one from the newly incremented value. The same broken change occured in machine_check_queue_event (which set a queue read by machine_check_process_queued_event). Fix that too, unbreaking printing of MCE information. Fixes: 69111bac42f5 ("powerpc: Replace __get_cpu_var uses") CC: Mahesh Salgaonkar CC: Christoph Lameter Signed-off-by: Daniel Axtens Signed-off-by: Michael Ellerman Signed-off-by: Kamal Mostafa --- arch/powerpc/kernel/mce.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c index 15c99b6..b2eb468 100644 --- a/arch/powerpc/kernel/mce.c +++ b/arch/powerpc/kernel/mce.c @@ -73,7 +73,7 @@ void save_mce_event(struct pt_regs *regs, long handled, uint64_t nip, uint64_t addr) { uint64_t srr1; - int index = __this_cpu_inc_return(mce_nest_count); + int index = __this_cpu_inc_return(mce_nest_count) - 1; struct machine_check_event *mce = this_cpu_ptr(&mce_event[index]); /* @@ -184,7 +184,7 @@ void machine_check_queue_event(void) if (!get_mce_event(&evt, MCE_EVENT_RELEASE)) return; - index = __this_cpu_inc_return(mce_queue_count); + index = __this_cpu_inc_return(mce_queue_count) - 1; /* If queue is full, just return for now. */ if (index >= MAX_MC_EVT) { __this_cpu_dec(mce_queue_count); -- 1.9.1