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 CCC31C433FF for ; Tue, 30 Jul 2019 11:12:06 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9D0A120693 for ; Tue, 30 Jul 2019 11:12:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D0A120693 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:59718 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hsQ33-0007SX-QZ for qemu-devel@archiver.kernel.org; Tue, 30 Jul 2019 07:12:05 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50307) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hsQ2U-0006ys-93 for qemu-devel@nongnu.org; Tue, 30 Jul 2019 07:11:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hsQ2T-0001NU-0K for qemu-devel@nongnu.org; Tue, 30 Jul 2019 07:11:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32806) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hsQ2Q-0001Ln-5N; Tue, 30 Jul 2019 07:11:26 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BFC284627A; Tue, 30 Jul 2019 11:11:24 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-51.ams2.redhat.com [10.36.116.51]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 13ED25C1B4; Tue, 30 Jul 2019 11:11:22 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 8A6B91138619; Tue, 30 Jul 2019 13:11:20 +0200 (CEST) From: Markus Armbruster To: Max Reitz References: <20190729164234.11573-1-kwolf@redhat.com> <874l34ghjm.fsf@dusky.pond.sub.org> <20190730082920.GA8134@localhost.localdomain> <0e04a847-bc0d-bd69-9dcc-f4c10f29d97d@redhat.com> Date: Tue, 30 Jul 2019 13:11:20 +0200 In-Reply-To: <0e04a847-bc0d-bd69-9dcc-f4c10f29d97d@redhat.com> (Max Reitz's message of "Tue, 30 Jul 2019 12:09:13 +0200") Message-ID: <87mugvdbfr.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Tue, 30 Jul 2019 11:11:24 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH for-4.1] scsi-cd: Fix inserting read-only media in empty drive X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , John Snow , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Max Reitz writes: > On 30.07.19 10:29, Kevin Wolf wrote: >> Am 30.07.2019 um 08:31 hat Markus Armbruster geschrieben: >>> Kevin Wolf writes: >>> >>>> scsi-disks decides whether it has a read-only device by looking at >>>> whether the BlockBackend specified as drive=3D... is read-only. In the >>>> case of an anonymous BlockBackend (with a node name specified in >>>> drive=3D...), this is the read-only flag of the attached node. In the = case >>>> of an empty anonymous BlockBackend, it's always read-write because >>>> nothing prevented it from being read-write. >>>> >>>> This is a problem because scsi-cd would take write permissions on the >>>> anonymous BlockBackend of an empty drive created without a drive=3D... >>>> option. Using blockdev-insert-medium with a read-only node fails then >>>> with the error message "Block node is read-only". >>>> >>>> Fix scsi_realize() so that scsi-cd devices always take read-only >>>> permissions on their BlockBackend instead. >>>> >>>> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=3D1733920 >>>> Signed-off-by: Kevin Wolf >>>> --- >>>> hw/scsi/scsi-disk.c | 10 ++++++++-- >>>> 1 file changed, 8 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c >>>> index 8e95e3e38d..af3e622dc5 100644 >>>> --- a/hw/scsi/scsi-disk.c >>>> +++ b/hw/scsi/scsi-disk.c >>>> @@ -2318,6 +2318,7 @@ static void scsi_disk_unit_attention_reported(SC= SIDevice *dev) >>>> static void scsi_realize(SCSIDevice *dev, Error **errp) >>>> { >>>> SCSIDiskState *s =3D DO_UPCAST(SCSIDiskState, qdev, dev); >>>> + bool read_only; >>>>=20=20 >>>> if (!s->qdev.conf.blk) { >>>> error_setg(errp, "drive property not set"); >>>> @@ -2351,8 +2352,13 @@ static void scsi_realize(SCSIDevice *dev, Error= **errp) >>>> return; >>>> } >>>> } >>>> - if (!blkconf_apply_backend_options(&dev->conf, >>>> - blk_is_read_only(s->qdev.conf.= blk), >>>> + >>>> + read_only =3D blk_is_read_only(s->qdev.conf.blk); >>>> + if (dev->type =3D=3D TYPE_ROM) { >>>> + read_only =3D true; >>>> + } >>>> + >>>> + if (!blkconf_apply_backend_options(&dev->conf, read_only, >>>> dev->type =3D=3D TYPE_DISK, er= rp)) { >>>> return; >>>> } >>> >>> For what it's worth, we have code similar to the one after this patch in >>> >>> * ide_dev_initfn() >>> >>> * xen_block_realize() (I guess) >>> >>> We have code similar to the one before this patch in >>> >>> * floppy_drive_realize() >>> >>> I figure we avoid the problem by recomputing read-only on media >>> change, in fd_change_cb(). Funny: looks like a medium's >>> read-only-ness lingers after unload until the next medium is loaded. >>=20 >> We may try to, but it looks something is broken for floppies. Ha! Cc: John. >> The bug only came to my attention yesterday, so I haven't got a full >> test case yet, but the half that I already have fails for floppy. I'll >> look into this, but it was more important to me to get at least the >> scsi-cd fix into 4.1. I think this patch is okay as a narrow fix for scsi-cd, thus Reviewed-by: Markus Armbruster >>> * nvme_realize() >>> >>> * virtio_blk_device_realize() >>> >>> * scsi_generic_realize() >>> >>> * usb_msd_storage_realize() >>> >>> Are these all okay? Should they work more like floppy? If not, what >>> makes floppy special? >>=20 >> Most of them aren't relevant in this context because this is a problem >> with removable media, and most devices don't support that. So as far as >> I know all we need to check is floppy, ATAPI and SCSI CD-ROM. >>=20 >> Floppy is special because it's the only read-write device that supports >> removable media (and you can insert a read-only floppy after ejecting a >> read-write one or vice versa). CDs can be simpler because they are >> always read-only. > > There are also SD cards. > > (The SD code just rejects read-only BBs, and it takes PERM_WRITE on it. > So I suppose it=E2=80=99s good because this way you simply can never ins= ert > read-only nodes.) I'd prefer to call this "differently broken" :)