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Mon, 2 Jul 2018 19:11:01 +0000 Received: from VI1PR07MB4254.eurprd07.prod.outlook.com ([fe80::44fe:35ff:4978:fb9d]) by VI1PR07MB4254.eurprd07.prod.outlook.com ([fe80::44fe:35ff:4978:fb9d%2]) with mapi id 15.20.0930.016; Mon, 2 Jul 2018 19:11:01 +0000 From: Kevin Darbyshire-Bryant To: Dave Taht CC: =?iso-8859-1?Q?Toke_H=F8iland-J=F8rgensen?= , Cake List Subject: Re: [Cake] Cake on openwrt - falling behind Thread-Topic: [Cake] Cake on openwrt - falling behind Thread-Index: AQHUEfzAVn4q46L7QUyKsSBc41C9maR8BF0AgAAXDQCAACjAgIAACK8A Date: Mon, 2 Jul 2018 19:11:01 +0000 Message-ID: <9F0353E5-D191-492A-9413-AA6BD03DD4C6@darbyshire-bryant.me.uk> References: <6DF9A5E0-EFD5-4519-9889-BC0A7B9BD48E@darbyshire-bryant.me.uk> <1A8BA286-6B31-4581-86C9-6855AC28C245@heistp.net> <673EAD3F-AB09-4B90-88BB-5DCE0BD65534@heistp.net> <6FE8D434-01BE-41A1-BD6B-EFFD67AC8784@heistp.net> <94C9790F-E9BC-4D59-9845-17C305E4B910@darbyshire-bryant.me.uk> <17AF79A0-0213-44E3-95B9-62795A644A47@heistp.net> <87lgatj13k.fsf@toke.dk> <87fu11ipir.fsf@toke.dk> In-Reply-To: Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: x-originating-ip: [2a02:c7f:1231:2000::dc83] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1; 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boundary="Apple-Mail=_ADC148C4-1114-43FE-BBEA-9ADECC8F3CC3"; protocol="application/pgp-signature"; micalg=pgp-sha256 MIME-Version: 1.0 X-OriginatorOrg: darbyshire-bryant.me.uk X-MS-Exchange-CrossTenant-Network-Message-Id: 75a2ca91-51b0-437c-88b4-08d5e04f8cfe X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Jul 2018 19:11:01.4072 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 9151708b-c553-406f-8e56-694f435154a4 X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR07MB3245 X-List-Received-Date: Mon, 02 Jul 2018 19:11:04 -0000 --Apple-Mail=_ADC148C4-1114-43FE-BBEA-9ADECC8F3CC3 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii > On 2 Jul 2018, at 19:39, Dave Taht wrote: >=20 >>=20 >=20 > This seems like it will introduce problems with stuff that isn't or is > legitimately broken in the first place, pointing to potentially random > data in the wrong place. >=20 > would a workaround be adding more padding to the cake stats output so > it's always even? >=20 > why does it work as written on arm? If I understand correctly: This will only be a problem on architectures = that require alignment of 64 bit values to 8 byte boundaries which is = achieved by padding the structure by a dummy (4 byte) value if required. = So to hit this bug we need kernel symbol = CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS undefined *and* we need a netlink = stats structure that needs a 4 byte dummy pad value to align to 8 bytes. = Of the architectures tested, MIPS is the only one that DOES NOT set = CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS and thus may be exposed to the = bug. arm sets CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS and thus no padding is = ever required/added, thus pointers always point to the correct data = location. --Apple-Mail=_ADC148C4-1114-43FE-BBEA-9ADECC8F3CC3 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEASyssijGxT6XdZEjs6I4m53iM0oFAls6eMQACgkQs6I4m53i M0qiCw//V2Vkfm/iYw8pb3dHRmQRqBty80YagYfIEaskWC7W7HGXH5wkZvteAfhr wCqk1smxBQkiwFcMtyQwtN1dy5lqe8GwVGCVi3VKSQoA8EUXPQLktjv4O6K10mto O7o9MfdrSWfocaxDzoplwTO0yZ5MMOlix1VVZLJs8CXQ0ktwVSjM198MWvMpe1De h3gRGsSkfJ2Z2w4wAMO5tXMBicGV6cBz69wuquJDLdpMggQ+e0jf6wHaQ6/Nt4Ee 3DMuQ0xpxrrvFrgRjPdjEKpD3yrE7mLR4/uZ7wDl0YhEEvoErjN/8n3O0eXEz4Xv HaXpIUshNOb85YAMEhDe58/gxjH5oBpL0MKbsqvI481BWz4VFp8ztn4esQJJ+PC1 WZqPnjCVW9FadOnK1h4jtjyybt8JeALYYtuwqqR1XlX+6zYMZVxrniK/KNYGOCUV PD7FJ42irDgVm/4vmszZU3rLwpWErlJ3DgD1OIB+5nqyYXVohHcoM2CDpSRVY0A4 wzgpkubNms2HFqgKqRgl8m/bEv99BRn89pTgvQby/HJjEVhgwkD4ZK2PoVRBb6dv 5JxVjjoSl3q+avJfG1QtAnskGNyb7Mx10U0uKyKlebqGMtO8NITyciCnIE9OTosQ yd5c+pVOuyJTXiYI9FyXyQeTQBglTXCVZf8ISjfF4NQdaNPKqDY= =Qf8a -----END PGP SIGNATURE----- --Apple-Mail=_ADC148C4-1114-43FE-BBEA-9ADECC8F3CC3--