From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751949AbeEDNzn (ORCPT ); Fri, 4 May 2018 09:55:43 -0400 Received: from foss.arm.com ([217.140.101.70]:53632 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751573AbeEDNzl (ORCPT ); Fri, 4 May 2018 09:55:41 -0400 From: Mark Rutland To: linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, aryabinin@virtuozzo.com, dvyukov@google.com, mark.rutland@arm.com, mingo@redhat.com, peterz@infradead.org Subject: [PATCH 0/3] kcov: fix unexpected faults Date: Fri, 4 May 2018 14:55:32 +0100 Message-Id: <20180504135535.53744-1-mark.rutland@arm.com> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, These patches fix a few issues where KCOV code could trigger recursive faults, discovered while debugging a patch enabling KCOV for arch/arm: * On CONFIG_PREEMPT kernels, there's a small race window where __sanitizer_cov_trace_pc() can see a bogus kcov_area. * Lazy faulting of the vmalloc area can cause mutual recursion between fault handling code and __sanitizer_cov_trace_pc(). * During the context switch, switching the mm can cause the kcov_area to be transiently unmapped. These are prerequisites for enabling KCOV on arm, but the issues themsevles are generic -- we just happen to avoid them by chance rather than design on x86-64 and arm64. I've tested this on arm atop of v4.17-rc3, with KCOV enabled. Thanks, Mark. Mark Rutland (3): kcov: ensure irq code sees a valid area kcov: prefault the kcov_area sched/core / kcov: avoid kcov_area during task switch include/linux/kcov.h | 14 ++++++++++++++ include/linux/sched.h | 2 +- kernel/kcov.c | 17 +++++++++++++++-- kernel/sched/core.c | 4 ++++ 4 files changed, 34 insertions(+), 3 deletions(-) -- 2.11.0