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Wed, 13 May 2020 07:43:39 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 48105A404D; Wed, 13 May 2020 07:43:39 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B16E9A4055; Wed, 13 May 2020 07:43:38 +0000 (GMT) Received: from localhost.localdomain (unknown [9.145.14.159]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 13 May 2020 07:43:38 +0000 (GMT) Subject: Re: [PATCH v1 2/8] s390/sclp: check sccb len before filling in data To: Cornelia Huck , David Hildenbrand References: <20200508230823.22956-1-walling@linux.ibm.com> <20200508230823.22956-3-walling@linux.ibm.com> <58bc496c-28bb-26f8-ab46-aba6ad141717@linux.ibm.com> <737869a8-13b2-1831-00c6-629d5a109d9c@redhat.com> <05ab2e59-10c0-c7df-c014-b54883ddccd3@linux.ibm.com> <9a39a948-91a1-7cfe-f2a5-d30e5564f318@redhat.com> <20200512180140.4be69d60.cohuck@redhat.com> From: Janosch Frank Autocrypt: addr=frankja@linux.ibm.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20200512180140.4be69d60.cohuck@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="54Ko7dESBoJ92ls0nJaYmy2kxEyCBCE5F" X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216, 18.0.676 definitions=2020-05-13_02:2020-05-11, 2020-05-13 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 mlxscore=0 priorityscore=1501 adultscore=0 clxscore=1015 malwarescore=0 spamscore=0 cotscore=-2147483648 phishscore=0 mlxlogscore=999 suspectscore=0 impostorscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005130065 Received-SPF: pass client-ip=148.163.158.5; envelope-from=frankja@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/13 03:43:44 X-ACL-Warn: Detected OS = Linux 3.x [generic] X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, KHOP_DYNAMIC=0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: Collin Walling , mst@redhat.com, qemu-devel@nongnu.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, qemu-s390x@nongnu.org, svens@linux.ibm.com, pbonzini@redhat.com, mihajlov@linux.ibm.com, rth@twiddle.net 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) --54Ko7dESBoJ92ls0nJaYmy2kxEyCBCE5F Content-Type: multipart/mixed; boundary="gMqlXQViMdHCPD8fA00C88VEVAUSyoV1s" --gMqlXQViMdHCPD8fA00C88VEVAUSyoV1s Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 5/12/20 6:01 PM, Cornelia Huck wrote: > On Mon, 11 May 2020 17:02:06 +0200 > David Hildenbrand wrote: >=20 >> On 11.05.20 16:50, Janosch Frank wrote: >>> On 5/11/20 4:44 PM, David Hildenbrand wrote: =20 >>>> On 11.05.20 16:36, Janosch Frank wrote: =20 >>>>> On 5/9/20 1:08 AM, Collin Walling wrote: =20 >>>>>> The SCCB must be checked for a sufficient length before it is fill= ed >>>>>> with any data. If the length is insufficient, then the SCLP comman= d >>>>>> is suppressed and the proper response code is set in the SCCB head= er. >>>>>> >>>>>> Signed-off-by: Collin Walling =20 >>>>> >>>>> Fixes tag? >=20 > Probably >=20 > Fixes: 832be0d8a3bb ("s390x: sclp: Report insufficient SCCB length") >=20 > ? >=20 >>>>> Reviewed-by: Janosch Frank =20 >>>> >>>> This is not a fix AFAIKs. >>>> sclp_service_call()/sclp_service_call_protected() always supplies a = full >>>> SCCB of exactly 4k size. >>>> =20 >>> >>> We don't check for QEMU's 4k buffer here, but for the length that was= >>> specified by the guest. >>> >>> It's valid for the guest to request cpu info and state that its buffe= r >>> is only 1k. We can't write everything in 1k if we have ~200 cpus, so >>> we'll report the insufficient length rc. >>> >>> What he fixes here is the time of the length check, it should be done= >>> before any changes are being done to the work_sccb. =20 >> >> I don't have access to the spec, especially, if the guest can expect >> nothing else in the sccb to change in case we report an error code. So= >> whatever you tell me, I have to trust you :) >=20 > Same here. Sounds plausible, but I have to trust the folks with the > documentation :) >=20 The AR states that: * Command validity check (has prio over length, as length is dependent on command) * boundary (if extended-length is not available) * Sufficient length check are done before "any other command action is taken". If a test fails the command is suppressed. --gMqlXQViMdHCPD8fA00C88VEVAUSyoV1s-- --54Ko7dESBoJ92ls0nJaYmy2kxEyCBCE5F Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEwGNS88vfc9+v45Yq41TmuOI4ufgFAl67pSoACgkQ41TmuOI4 ufgkCw//cMC3uNJ5TiAQ3A07dP+oroL5YF9IkXTLZ9I+Mn6lKLgMmdv4RJnVut1X eGQcKvqdyiwpScMNbMXWI5a/uIBkDLjP9N/yyhseUNVuQaf9pty1bkC1DdaOFdw/ dUpVmEqCWgeZKn3hp0eL5avUZSQ4sNDbVZPC0dAqFuW4/nEXwEwa/+tT4v/rLs8C AdK1C3//GViH092CoSNSH0IGTjnLClsi7EqH/89AASDh0DnDzMVCUycpkgh0KRkF GUb7z6vvIV748qHhpbghio221u1BS0FtRYFFjwO/45Krpine/zS2/rtVKYBFfXf7 b/MVZPjo/RAX2/aSQ0jTSFQzrIoOVatCO0AmT/Xn4wputeKLQoLihCVsHY2SwYHT lJAjVfvcqMpo16S7r2lhL+V1tARii01aMLtv/Zs8vzJCznGoMmtpFJYAr9g73tps iinhvIHXb2HML3k9BdZVnoJyEFUGlYD8trB7TQgBvj49CHWeJsEEP2GlY3vIicfR tOMMA9RlhB55EU48+PkpHH8ihDgMrS3ZcjoNbebeXgyL1yy25oAeueTEQNz/nLrE 9AihffwfRvbBJX/xEvAI2dfjRKzD+ScHcyMF96ZSvpPu96sHAeSdTE7Iefb91m5j jrIntRRCj8Jw1nX/x9cFlrlyJp0QXLmcZ/oXO9qCnZrm5Rq9sKA= =VvwJ -----END PGP SIGNATURE----- --54Ko7dESBoJ92ls0nJaYmy2kxEyCBCE5F--