From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48B68C433FF for ; Tue, 30 Jul 2019 11:37:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1EAC9206E0 for ; Tue, 30 Jul 2019 11:37:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730667AbfG3LhW (ORCPT ); Tue, 30 Jul 2019 07:37:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60590 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730616AbfG3LhV (ORCPT ); Tue, 30 Jul 2019 07:37:21 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 646513082B1F; Tue, 30 Jul 2019 11:37:21 +0000 (UTC) Received: from dhcp201-121.englab.pnq.redhat.com (ovpn-116-177.sin2.redhat.com [10.67.116.177]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7DCED60856; Tue, 30 Jul 2019 11:37:12 +0000 (UTC) From: Pankaj Gupta To: snitzer@redhat.com, dan.j.williams@intel.com Cc: dm-devel@redhat.com, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, agk@redhat.com, pagupta@redhat.com Subject: [PATCH] dm: fix dax_dev NULL dereference Date: Tue, 30 Jul 2019 17:07:08 +0530 Message-Id: <20190730113708.14660-1-pagupta@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Tue, 30 Jul 2019 11:37:21 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 'Murphy Zhou' reports[1] hitting the panic when running xfstests generic/108 on pmem ramdisk. In his words: This test is simulating partial disk error when calling fsync(): create a lvm vg which consists of 2 disks: one scsi_debug disk; one other disk I specified, pmem ramdisk in this case. create lv in this vg and write to it, make sure writing across 2 disks; offline scsi_debug disk; write again to allocated area; expect fsync: IO error. If one of the disks is pmem ramdisk, it reproduces every time on my setup, on v5.3-rc2+. The mount -o dax option is not required to reproduce this panic. ... Fix this by returning false from 'device_synchronous' function when dax_dev is NULL. [ 1984.878208] BUG: kernel NULL pointer dereference, address: 00000000000002d0 [ 1984.882546] #PF: supervisor read access in kernel mode [ 1984.885664] #PF: error_code(0x0000) - not-present page [ 1984.888626] PGD 0 P4D 0 [ 1984.890140] Oops: 0000 [#1] SMP PTI ... ... [ 1984.943682] Call Trace: [ 1984.945007] device_synchronous+0xe/0x20 [dm_mod] [ 1984.947328] stripe_iterate_devices+0x48/0x60 [dm_mod] [ 1984.949947] ? dm_set_device_limits+0x130/0x130 [dm_mod] [ 1984.952516] dm_table_supports_dax+0x39/0x90 [dm_mod] [ 1984.954989] dm_table_set_restrictions+0x248/0x5d0 [dm_mod] [ 1984.957685] dm_setup_md_queue+0x66/0x110 [dm_mod] [ 1984.960280] table_load+0x1e3/0x390 [dm_mod] [ 1984.962491] ? retrieve_status+0x1c0/0x1c0 [dm_mod] [ 1984.964910] ctl_ioctl+0x1d3/0x550 [dm_mod] [ 1984.967006] ? path_lookupat+0xf4/0x200 [ 1984.968890] dm_ctl_ioctl+0xa/0x10 [dm_mod] [ 1984.970920] do_vfs_ioctl+0xa9/0x630 [ 1984.972701] ksys_ioctl+0x60/0x90 [ 1984.974335] __x64_sys_ioctl+0x16/0x20 [ 1984.976221] do_syscall_64+0x5b/0x1d0 [ 1984.978091] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [1] https://lore.kernel.org/linux-fsdevel/2011806368.5335560.1564469373050.JavaMail.zimbra@redhat.com/T/#mac662eb50b9d7bd282b23e6e8625a3f7a4687506 Fixes: 2e9ee0955d3c ("dm: enable synchronous dax") Reported-by: jencce.kernel@gmail.com Tested-by: jencce.kernel@gmail.com Signed-off-by: Pankaj Gupta --- drivers/md/dm-table.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index caaee8032afe..b065845c1bdd 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -894,6 +894,9 @@ int device_supports_dax(struct dm_target *ti, struct dm_dev *dev, static int device_synchronous(struct dm_target *ti, struct dm_dev *dev, sector_t start, sector_t len, void *data) { + if (!dev->dax_dev) + return false; + return dax_synchronous(dev->dax_dev); } -- 2.20.1