From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756803Ab3KYN7G (ORCPT ); Mon, 25 Nov 2013 08:59:06 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:58964 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753891Ab3KYNxz (ORCPT ); Mon, 25 Nov 2013 08:53:55 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "John David Anglin" , "Helge Deller" Date: Mon, 25 Nov 2013 13:44:29 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 65/87] parisc: fix interruption handler to respect pagefault_disable() In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.212 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.53-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Helge Deller commit 59b33f148cc08fb33cbe823fca1e34f7f023765e upstream. Running an "echo t > /proc/sysrq-trigger" crashes the parisc kernel. The problem is, that in print_worker_info() we try to read the workqueue info via the probe_kernel_read() functions which use pagefault_disable() to avoid crashes like this: probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq)); probe_kernel_read(&wq, &pwq->wq, sizeof(wq)); probe_kernel_read(name, wq->name, sizeof(name) - 1); The problem here is, that the first probe_kernel_read(&pwq) might return zero in pwq and as such the following probe_kernel_reads() try to access contents of the page zero which is read protected and generate a kernel segfault. With this patch we fix the interruption handler to call parisc_terminate() directly only if pagefault_disable() was not called (in which case preempt_count()==0). Otherwise we hand over to the pagefault handler which will try to look up the faulting address in the fixup tables. Signed-off-by: Helge Deller Signed-off-by: John David Anglin Signed-off-by: Helge Deller Signed-off-by: Ben Hutchings --- arch/parisc/kernel/traps.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/arch/parisc/kernel/traps.c +++ b/arch/parisc/kernel/traps.c @@ -811,14 +811,14 @@ void notrace handle_interruption(int cod else { /* - * The kernel should never fault on its own address space. + * The kernel should never fault on its own address space, + * unless pagefault_disable() was called before. */ - if (fault_space == 0) + if (fault_space == 0 && !in_atomic()) { pdc_chassis_send_status(PDC_CHASSIS_DIRECT_PANIC); parisc_terminate("Kernel Fault", regs, code, fault_address); - } }