From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757722AbcHCCwJ (ORCPT ); Tue, 2 Aug 2016 22:52:09 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:33112 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757694AbcHCCvz (ORCPT ); Tue, 2 Aug 2016 22:51:55 -0400 To: Russell King From: Guenter Roeck Subject: "Failed to create /dev/root: -14" after commit e6978e4bf1 ("ARM: save and reset the address limit when entering an exception") Cc: "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Will Deacon Message-ID: <57A15C41.6000804@roeck-us.net> Date: Tue, 2 Aug 2016 19:51:45 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I see the following crash when running a qemu arm 'kzm' runtime test with the current mainline. Failed to create /dev/root: -14 [ followed by panic ] A complete log file is at [1]. Bisect points to commit e6978e4bf1 ("ARM: save and reset the address limit when entering an exception"). Some additional debugging shows lots of similar error returns from strncpy_from_user(). For the error case resulting in the crash, the call chain is as follows. sys_mknod sys_mknodat() user_path_create() getname() getname_flags() strncpy_from_user() Reverting the patch fixes the problem. I don't see the problem with any other qemu arm test. It looks like the kernel runs in exception context. My gut feeling is that qemu may be to blame, but I am not really sure. Any idea how to track this down ? Thanks, Guenter --- [1] http://kerneltests.org/builders/qemu-arm-master/builds/615