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Mon, 13 Jul 2020 10:10:59 +0000 (UTC) Subject: Re: [PATCH] block: Raise an error when backing file parameter is an empty string To: Connor Kuehl , kwolf@redhat.com References: <20200617182725.951119-1-ckuehl@redhat.com> From: Max Reitz Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: <32e25922-c3da-c3a6-c853-c729a3a85853@redhat.com> Date: Mon, 13 Jul 2020 12:10:57 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200617182725.951119-1-ckuehl@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="xQuMvF8HZMvt1mvvDOW3DZGo5uiHDwAqO" Received-SPF: pass client-ip=205.139.110.61; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/13 01:36:29 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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: qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --xQuMvF8HZMvt1mvvDOW3DZGo5uiHDwAqO Content-Type: multipart/mixed; boundary="6pUGHUTAabwjd6zODCk5nROiza3jjJa7M" --6pUGHUTAabwjd6zODCk5nROiza3jjJa7M Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 17.06.20 20:27, Sorry :/ Connor Kuehl wrote: > Providing an empty string for the backing file parameter like so: >=20 > =09qemu-img create -f qcow2 -b '' /tmp/foo >=20 > allows the flow of control to reach and subsequently fail an assert > statement because passing an empty string to >=20 > =09bdrv_get_full_backing_filename_from_filename() >=20 > simply results in NULL being returned without an error being raised. >=20 > To fix this, let's check for an empty string when getting the value from > the opts list. >=20 > Reported-by: Attila Fazekas > Fixes: https://bugzilla.redhat.com/1809553 > Signed-off-by: Connor Kuehl > --- > block.c | 4 ++++ > tests/qemu-iotests/298 | 47 ++++++++++++++++++++++++++++++++++++++ > tests/qemu-iotests/298.out | 5 ++++ > tests/qemu-iotests/group | 1 + > 4 files changed, 57 insertions(+) > create mode 100755 tests/qemu-iotests/298 > create mode 100644 tests/qemu-iotests/298.out >=20 > diff --git a/block.c b/block.c > index 6dbcb7e083..b335d6bcb2 100644 > --- a/block.c > +++ b/block.c > @@ -6116,6 +6116,10 @@ void bdrv_img_create(const char *filename, const c= har *fmt, > "same filename as the backing file"); > goto out; > } > + if (backing_file[0] =3D=3D '\0') { > + error_setg(errp, "Expected backing file name, got empty stri= ng"); > + goto out; > + } Looks good. > } > =20 > backing_fmt =3D qemu_opt_get(opts, BLOCK_OPT_BACKING_FMT); > diff --git a/tests/qemu-iotests/298 b/tests/qemu-iotests/298 > new file mode 100755 > index 0000000000..1e30caebec > --- /dev/null > +++ b/tests/qemu-iotests/298 > @@ -0,0 +1,47 @@ > +#!/usr/bin/env python3 > +# > +# Copyright (C) 2020 Red Hat, Inc. > +# > +# This program is free software; you can redistribute it and/or modify > +# it under the terms of the GNU General Public License as published by > +# the Free Software Foundation; either version 2 of the License, or > +# (at your option) any later version. > +# > +# This program is distributed in the hope that it will be useful, > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > +# GNU General Public License for more details. > +# > +# You should have received a copy of the GNU General Public License > +# along with this program. If not, see . > + > + > + > +# Regression test for avoiding an assertion when the 'backing file' > +# parameter (-b) is set to an empty string for qemu-img create > +# > +# qemu-img create -f qcow2 -b '' /tmp/foo > +# > +# This ensures the invalid parameter is handled with a user- > +# friendly message instead of a failed assertion. > + > +import iotests > + > +class TestEmptyBackingFilename(iotests.QMPTestCase): > + > + > + def test_empty_backing_file_name(self): > + actual =3D iotests.qemu_img_pipe( (pylint complains about the indentation that follows, it says it=E2=80=99d prefer four spaces less. Make of that want you wish, AFAIA there=E2=80=99s= no requirement to get a clean pylint pass for iotests yet. O:)) > + 'create', > + '-f', 'qcow2', This should be iotests.imgfmt, not specifically qcow2. > + '-b', '', > + '/tmp/foo' I=E2=80=99m not sure I like using /tmp/foo very much, for two reasons: Firs= t, this expects that the backing filename will be checked before something really happens with the image filename; for example on Windows, /tmp/foo is just not a valid filename, so we might end up getting an error because of that. Or, for me, I like saving mails in a directory called /tmp/foo, so maybe at some point I get an error because /tmp/foo already exists as a directory. Second, if we ever do run into a regression or some configuration where this test unexpectedly manages to create the image, it would overwrite /tmp/foo. Which maybe isn=E2=80=99t good, because maybe it=E2=80=99s a fil= e the user wants to keep around. The fix is simple, just use some file under iotests.test_dir. I think the easiest way right now is something like: with iotests.FilePath('test.img') as img_path: actual =3D iotests.qemu_img_pipe('create', ..., img_path, '1M') expected =3D f'qemu-img: {img_path}: Expected...' self.assertEqual(...) (On that note, I=E2=80=99d give a size to qemu-img, so that the invocation = is correct apart from the missing backing file name.) > + ) > + expected =3D 'qemu-img: /tmp/foo: Expected backing file name,' \ > + ' got empty string' > + > + self.assertEqual(actual.strip(), expected.strip()) > + > + > +if __name__ =3D=3D '__main__': > + iotests.main(supported_fmts=3D['raw', 'qcow2']) raw isn=E2=80=99t supported, this test only works for formats that support backing files. (Which also means it should work for qed and qcow, I imagine...?) Max --6pUGHUTAabwjd6zODCk5nROiza3jjJa7M-- --xQuMvF8HZMvt1mvvDOW3DZGo5uiHDwAqO Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl8MMzEACgkQ9AfbAGHV z0AvvQf+Mc2vXpS1XfcFwYyR0nu7I8tetQ5LEddGSVnSk9YXe4LEXgl2Iz0irMgl WypA3+AAFqiv6vW36bOYiCx819d9fH3OA8DGLcVFgSA/tz4H9AxBGq0i8/bxQzDh 6kA5rAry5w5ls7+EhE5+0jnbkQp+nD1XJftRVXas1cVLilWZv6IjvxEoNoidpKp0 8OV5f8KEV1R7VHWG5bZ5d0Rqv7BbxPh5FlOfMWzYEwaep+1A+FmZRAdGTSGMOyBK o+VPE7bITiLTi8qZO5iIq1jrXXtV2bOAaQf6ylgq+XGlf9dzsc36d4FHED9QjTL1 IISvHKcF4VIEx+1T7EW/snkR/wIuzA== =kX0R -----END PGP SIGNATURE----- --xQuMvF8HZMvt1mvvDOW3DZGo5uiHDwAqO--