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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 9429BC433DB for ; Fri, 29 Jan 2021 07:35:32 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 4761D64DA1 for ; Fri, 29 Jan 2021 07:35:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4761D64DA1 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.77740.140989 (Exim 4.92) (envelope-from ) id 1l5OJD-0001BS-Or; Fri, 29 Jan 2021 07:35:11 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 77740.140989; Fri, 29 Jan 2021 07:35:11 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l5OJD-0001BL-LM; Fri, 29 Jan 2021 07:35:11 +0000 Received: by outflank-mailman (input) for mailman id 77740; Fri, 29 Jan 2021 07:35:09 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l5OJB-0001BG-Nt for xen-devel@lists.xenproject.org; Fri, 29 Jan 2021 07:35:09 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id e94c1306-46b8-4030-9b95-5d1484d3ea0e; Fri, 29 Jan 2021 07:35:08 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 65E32ABDA; Fri, 29 Jan 2021 07:35:07 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: e94c1306-46b8-4030-9b95-5d1484d3ea0e X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1611905707; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=zAq51H83aYnizsU5uKH4Xo3JZYjQqCAFMXuwsnbMpLQ=; b=egkOuZgO/1U3ZcJB0aoekc8YSPYrBM6Dbx4wpJ7qyPhKX7f9X3H2cqMyawp7VD5rpT7YDZ URDzYzj3ypDwVGagHUmRlb6Wjj7WevT/XncPuMIRgZh+8067dnTdjTLZ9dAXKQn7fdCkXZ 665Pk57zhHySUtiPYi9FUeK8y3atlLE= Subject: Re: [PATCH v2] xen-blkback: fix compatibility bug with single page rings To: Dongli Zhang , Paul Durrant , xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Paul Durrant , Konrad Rzeszutek Wilk , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Jens Axboe References: <20210128130441.11744-1-paul@xen.org> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <7fb64e2f-141a-c848-0f8a-2313d2e821b6@suse.com> Date: Fri, 29 Jan 2021 08:35:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="KTNhVyFFfyx2e8FCQZ7SGPr0cJJ2X0WH9" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --KTNhVyFFfyx2e8FCQZ7SGPr0cJJ2X0WH9 Content-Type: multipart/mixed; boundary="v0ECwaP7zIbuMUDrGMvLowgnhMmWanZZI"; protected-headers="v1" From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= To: Dongli Zhang , Paul Durrant , xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Paul Durrant , Konrad Rzeszutek Wilk , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Jens Axboe Message-ID: <7fb64e2f-141a-c848-0f8a-2313d2e821b6@suse.com> Subject: Re: [PATCH v2] xen-blkback: fix compatibility bug with single page rings References: <20210128130441.11744-1-paul@xen.org> In-Reply-To: --v0ECwaP7zIbuMUDrGMvLowgnhMmWanZZI Content-Type: multipart/mixed; boundary="------------23E2E4DE08DE09AA38981101" Content-Language: en-US This is a multi-part message in MIME format. --------------23E2E4DE08DE09AA38981101 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 29.01.21 07:20, Dongli Zhang wrote: >=20 >=20 > On 1/28/21 5:04 AM, Paul Durrant wrote: >> From: Paul Durrant >> >> Prior to commit 4a8c31a1c6f5 ("xen/blkback: rework connect_ring() to a= void >> inconsistent xenstore 'ring-page-order' set by malicious blkfront"), t= he >> behaviour of xen-blkback when connecting to a frontend was: >> >> - read 'ring-page-order' >> - if not present then expect a single page ring specified by 'ring-ref= ' >> - else expect a ring specified by 'ring-refX' where X is between 0 and= >> 1 << ring-page-order >> >> This was correct behaviour, but was broken by the afforementioned comm= it to >> become: >> >> - read 'ring-page-order' >> - if not present then expect a single page ring (i.e. ring-page-order = =3D 0) >> - expect a ring specified by 'ring-refX' where X is between 0 and >> 1 << ring-page-order >> - if that didn't work then see if there's a single page ring specified= by >> 'ring-ref' >> >> This incorrect behaviour works most of the time but fails when a front= end >> that sets 'ring-page-order' is unloaded and replaced by one that does = not >> because, instead of reading 'ring-ref', xen-blkback will read the stal= e >> 'ring-ref0' left around by the previous frontend will try to map the w= rong >> grant reference. >> >> This patch restores the original behaviour. >> >> Fixes: 4a8c31a1c6f5 ("xen/blkback: rework connect_ring() to avoid inco= nsistent xenstore 'ring-page-order' set by malicious blkfront") >> Signed-off-by: Paul Durrant >> --- >> Cc: Konrad Rzeszutek Wilk >> Cc: "Roger Pau Monn=C3=A9" >> Cc: Jens Axboe >> Cc: Dongli Zhang >> >> v2: >> - Remove now-spurious error path special-case when nr_grefs =3D=3D 1= >> --- >> drivers/block/xen-blkback/common.h | 1 + >> drivers/block/xen-blkback/xenbus.c | 38 +++++++++++++---------------= -- >> 2 files changed, 17 insertions(+), 22 deletions(-) >> >> diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-bl= kback/common.h >> index b0c71d3a81a0..524a79f10de6 100644 >> --- a/drivers/block/xen-blkback/common.h >> +++ b/drivers/block/xen-blkback/common.h >> @@ -313,6 +313,7 @@ struct xen_blkif { >> =20 >> struct work_struct free_work; >> unsigned int nr_ring_pages; >> + bool multi_ref; >=20 > Is it really necessary to introduce 'multi_ref' here or we may just re-= use > 'nr_ring_pages'? >=20 > According to blkfront code, 'ring-page-order' is set only when it is no= t zero, > that is, only when (info->nr_ring_pages > 1). Did you look into all other OS's (Windows, OpenBSD, FreebSD, NetBSD, Solaris, Netware, other proprietary systems) implementations to verify that claim? I don't think so. So better safe than sorry. Juergen --------------23E2E4DE08DE09AA38981101 Content-Type: application/pgp-keys; name="OpenPGP_0xB0DE9DD628BF132F.asc" Content-Transfer-Encoding: quoted-printable Content-Disposition: attachment; filename="OpenPGP_0xB0DE9DD628BF132F.asc" -----BEGIN PGP PUBLIC KEY BLOCK----- xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOBy= cWx w3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJvedYm8O= f8Z d621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJNwQpd369y= 9bf IhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvxXP3FAp2pkW0xq= G7/ 377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEBAAHNHEp1ZXJnZW4gR= 3Jv c3MgPGpnQHBmdXBmLm5ldD7CwHkEEwECACMFAlOMcBYCGwMHCwkIBwMCAQYVCAIJCgsEFgIDA= QIe AQIXgAAKCRCw3p3WKL8TL0KdB/93FcIZ3GCNwFU0u3EjNbNjmXBKDY4FUGNQH2lvWAUy+dnyT= hpw dtF/jQ6j9RwE8VP0+NXcYpGJDWlNb9/JmYqLiX2Q3TyevpB0CA3dbBQp0OW0fgCetToGIQrg0= MbD 1C/sEOv8Mr4NAfbauXjZlvTj30H2jO0u+6WGM6nHwbh2l5O8ZiHkH32iaSTfN7Eu5RnNVUJbv= oPH Z8SlM4KWm8rG+lIkGurqqu5gu8q8ZMKdsdGC4bBxdQKDKHEFExLJK/nRPFmAuGlId1E3fe10v= 5QL +qHI3EIPtyfE7i9Hz6rVwi7lWKgh7pe0ZvatAudZ+JNIlBKptb64FaiIOAWDCx1SzR9KdWVyZ= 2Vu IEdyb3NzIDxqZ3Jvc3NAc3VzZS5jb20+wsB5BBMBAgAjBQJTjHCvAhsDBwsJCAcDAgEGFQgCC= QoL BBYCAwECHgECF4AACgkQsN6d1ii/Ey/HmQf/RtI7kv5A2PS4RF7HoZhPVPogNVbC4YA6lW7Dr= Wf0 teC0RR3MzXfy6pJ+7KLgkqMlrAbN/8Dvjoz78X+5vhH/rDLa9BuZQlhFmvcGtCF8eR0T1v0nC= /nu AFVGy+67q2DH8As3KPu0344TBDpAvr2uYM4tSqxK4DURx5INz4ZZ0WNFHcqsfvlGJALDeE0Lh= ITT d9jLzdDad1pQSToCnLl6SBJZjDOX9QQcyUigZFtCXFst4dlsvddrxyqT1f17+2cFSdu7+ynLm= XBK 7abQ3rwJY8SbRO2iRulogc5vr/RLMMlscDAiDkaFQWLoqHHOdfO9rURssHNN8WkMnQfvUewRz= 80h SnVlcmdlbiBHcm9zcyA8amdyb3NzQG5vdmVsbC5jb20+wsB5BBMBAgAjBQJTjHDXAhsDBwsJC= AcD AgEGFQgCCQoLBBYCAwECHgECF4AACgkQsN6d1ii/Ey8PUQf/ehmgCI9jB9hlgexLvgOtf7PJn= FOX gMLdBQgBlVPO3/D9R8LtF9DBAFPNhlrsfIG/SqICoRCqUcJ96Pn3P7UUinFG/I0ECGF4EvTE1= jnD kfJZr6jrbjgyoZHiw/4BNwSTL9rWASyLgqlA8u1mf+c2yUwcGhgkRAd1gOwungxcwzwqgljf0= N51 N5JfVRHRtyfwq/ge+YEkDGcTU6Y0sPOuj4Dyfm8fJzdfHNQsWq3PnczLVELStJNdapwPOoE+l= otu fe3AM2vAEYJ9rTz3Cki4JFUsgLkHFqGZarrPGi1eyQcXeluldO3m91NK/1xMI3/+8jbO0tsn1= tqS EUGIJi7ox80eSnVlcmdlbiBHcm9zcyA8amdyb3NzQHN1c2UuZGU+wsB5BBMBAgAjBQJTjHDrA= hsD BwsJCAcDAgEGFQgCCQoLBBYCAwECHgECF4AACgkQsN6d1ii/Ey+LhQf9GL45eU5vOowA2u5N3= g3O ZUEBmDHVVbqMtzwlmNC4k9Kx39r5s2vcFl4tXqW7g9/ViXYuiDXb0RfUpZiIUW89siKrkzmQ5= dM7 wRqzgJpJwK8Bn2MIxAKArekWpiCKvBOB/Cc+3EXE78XdlxLyOi/NrmSGRIov0karw2RzMNOu5= D+j LRZQd1Sv27AR+IP3I8U4aqnhLpwhK7MEy9oCILlgZ1QZe49kpcumcZKORmzBTNh30FVKK1Evm= V2x AKDoaEOgQB4iFQLhJCdP1I5aSgM5IVFdn7v5YgEYuJYx37IoN1EblHI//x/e2AaIHpzK5h88N= Eaw QsaNRpNSrcfbFmAg987ATQRTjHAWAQgAyzH6AOODMBjgfWE9VeCgsrwH3exNAU32gLq2xvjpW= nHI s98ndPUDpnoxWQugJ6MpMncr0xSwFmHEgnSEjK/PAjppgmyc57BwKII3sV4on+gDVFJR6Y8ZR= wgn BC5mVM6JjQ5xDk8WRXljExRfUX9pNhdE5eBOZJrDRoLUmmjDtKzWaDhIg/+1Hzz93X4fCQkNV= bVF LELU9bMaLPBG/x5q4iYZ2k2ex6d47YE1ZFdMm6YBYMOljGkZKwYde5ldM9mo45mmwe0icXKLk= pEd IXKTZeKDO+Hdv1aqFuAcccTg9RXDQjmwhC3yEmrmcfl0+rPghO0Iv3OOImwTEe4co3c1mwARA= QAB wsBfBBgBAgAJBQJTjHAWAhsMAAoJELDendYovxMvQ/gH/1ha96vm4P/L+bQpJwrZ/dneZcmEw= Tbe 8YFsw2V/Buv6Z4Mysln3nQK5ZadD534CF7TDVft7fC4tU4PONxF5D+/tvgkPfDAfF77zy2AH1= vJz Q1fOU8lYFpZXTXIHb+559UqvIB8AdgR3SAJGHHt4RKA0F7f5ipYBBrC6cyXJyyoprT10EMvU8= VGi wXvTyJz3fjoYsdFzpWPlJEBRMedCot60g5dmbdrZ5DWClAr0yau47zpWj3enf1tLWaqcsuylW= svi uGjKGw7KHQd3bxALOknAp4dN3QwBYCKuZ7AddY9yjynVaD5X7nF9nO5BjR/i1DG86lem3iBDX= zXs ZDn8R38=3D =3D2wuH -----END PGP PUBLIC KEY BLOCK----- --------------23E2E4DE08DE09AA38981101-- --v0ECwaP7zIbuMUDrGMvLowgnhMmWanZZI-- --KTNhVyFFfyx2e8FCQZ7SGPr0cJJ2X0WH9 Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature" -----BEGIN PGP SIGNATURE----- wsB5BAABCAAjFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAmATuqoFAwAAAAAACgkQsN6d1ii/Ey80 kwf/e41zDqm+jP5oJsLO4FvTwwwFeSs6ARV+zlLQCldBq5oB1HPuzNpjQsE704m/eUEZzMZy2/7W Z1pKAwvSLzPQyyx7Rw8pJKJuNio7oIAiCKAiupU3rJBmorI3CCLlbpwfdFGkuKJ8GxZs193BL+WC 3dNKyBC4aFT3khnmT5y/9PF08Ms9YYVOYPq+6KOM0MbsseD9d4E9LwsC1wzWG9EUA5Ckh8wIZ3XR VO1561Q2S36zukXwzbvsGOk9JmD/1kjjR26wsC0JAYU5JKIJxAeeR9V1ZXXrcLjbmwC8KPF+mhOP /9Obe9R6O6mT4jKwbmwqJBYjBBJvMsSkKdry2YZZRg== =KyR6 -----END PGP SIGNATURE----- --KTNhVyFFfyx2e8FCQZ7SGPr0cJJ2X0WH9--