From patchwork Thu Nov 19 13:02:19 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vitaly Kuznetsov X-Patchwork-Id: 7657121 Return-Path: X-Original-To: patchwork-linux-scsi@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 1CD03BF90C for ; Thu, 19 Nov 2015 13:02:39 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 38C83206AB for ; Thu, 19 Nov 2015 13:02:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 59783206AA for ; Thu, 19 Nov 2015 13:02:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757732AbbKSNCX (ORCPT ); Thu, 19 Nov 2015 08:02:23 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53539 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753286AbbKSNCW (ORCPT ); Thu, 19 Nov 2015 08:02:22 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (Postfix) with ESMTPS id AB84AE7095; Thu, 19 Nov 2015 13:02:22 +0000 (UTC) Received: from vitty.brq.redhat.com (vitty.brq.redhat.com [10.34.26.3]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id tAJD2KMb008530; Thu, 19 Nov 2015 08:02:20 -0500 From: Vitaly Kuznetsov To: "James E.J. Bottomley" Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, "K. Y. Srinivasan" , Bart Van Assche Subject: [PATCH RESEND_2] scsi_sysfs: protect against double execution of __scsi_remove_device() Date: Thu, 19 Nov 2015 14:02:19 +0100 Message-Id: <1447938139-22072-1-git-send-email-vkuznets@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On some host errors storvsc module tries to remove sdev by scheduling a job which does the following: sdev = scsi_device_lookup(wrk->host, 0, 0, wrk->lun); if (sdev) { scsi_remove_device(sdev); scsi_device_put(sdev); } While this code seems correct the following crash is observed: general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC RIP: 0010:[] [] bdi_destroy+0x39/0x220 ... [] ? _raw_spin_unlock_irq+0x2c/0x40 [] blk_cleanup_queue+0x17b/0x270 [] __scsi_remove_device+0x54/0xd0 [scsi_mod] [] scsi_remove_device+0x2b/0x40 [scsi_mod] [] storvsc_remove_lun+0x3d/0x60 [hv_storvsc] [] process_one_work+0x1b1/0x530 ... The problem comes with the fact that many such jobs (for the same device) are being scheduled simultaneously. While scsi_remove_device() uses shost->scan_mutex and scsi_device_lookup() will fail for a device in SDEV_DEL state there is no protection against someone who did scsi_device_lookup() before we actually entered __scsi_remove_device(). So the whole scenario looks like that: two callers do simultaneous (or preemption happens) calls to scsi_device_lookup() ant these calls succeed for both of them, after that they try doing scsi_remove_device(). shost->scan_mutex only serializes their calls to __scsi_remove_device() and we end up doing the cleanup path twice. Signed-off-by: Vitaly Kuznetsov Reviewed-by: Christoph Hellwig --- drivers/scsi/scsi_sysfs.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 8d23122..905dd1c 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -1102,6 +1102,14 @@ void __scsi_remove_device(struct scsi_device *sdev) { struct device *dev = &sdev->sdev_gendev; + /* + * This cleanup path is not reentrant and while it is impossible + * to get a new reference with scsi_device_get() someone can still + * hold a previously acquired one. + */ + if (sdev->sdev_state == SDEV_DEL) + return; + if (sdev->is_visible) { if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0) return;