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[40.107.78.58]) by mx.google.com with ESMTPS id 48si8508521otg.161.2019.02.05.09.55.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 05 Feb 2019 09:55:02 -0800 (PST) Received-SPF: pass (google.com: domain of namit@vmware.com designates 40.107.78.58 as permitted sender) client-ip=40.107.78.58; Authentication-Results: mx.google.com; dkim=pass header.i=@vmware.com header.s=selector1 header.b=OpAGewTa; spf=pass (google.com: domain of namit@vmware.com designates 40.107.78.58 as permitted sender) smtp.mailfrom=namit@vmware.com; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=vmware.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=vmware.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=DvX0SvjzS9cg6KCABhOsPWSCOuOybvRlHZr0Cemjf4M=; b=OpAGewTadxIiu2tMElin5owl7CWsCVVrijVMnRG6Pthy8Zdi1OfGb8jRXisJK8MdhqZFGho3dHnHLTlJBmPRrn8ZxrZhf3Ol53iQFg0sFuknEJUGQRj+E27JmJYsrepyunMK+Dkti5KARvgxwX65eZuQYgRlzJpxYwnGf5wNiR8= Received: from BYAPR05MB4776.namprd05.prod.outlook.com (52.135.233.146) by BYAPR05MB6296.namprd05.prod.outlook.com (20.178.51.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.1601.15; Tue, 5 Feb 2019 17:54:57 +0000 Received: from BYAPR05MB4776.namprd05.prod.outlook.com ([fe80::99ab:18fb:f393:df31]) by BYAPR05MB4776.namprd05.prod.outlook.com ([fe80::99ab:18fb:f393:df31%3]) with mapi id 15.20.1601.016; Tue, 5 Feb 2019 17:54:57 +0000 From: Nadav Amit To: Borislav Petkov CC: Peter Zijlstra , Rick Edgecombe , Andy Lutomirski , Ingo Molnar , LKML , X86 ML , "H. Peter Anvin" , Thomas Gleixner , Dave Hansen , Damian Tometzki , linux-integrity , LSM List , Andrew Morton , Kernel Hardening , Linux-MM , Will Deacon , Ard Biesheuvel , Kristen Carlson Accardi , "Dock, Deneen T" , Kees Cook , Dave Hansen , Masami Hiramatsu Subject: Re: [PATCH v2 06/20] x86/alternative: use temporary mm for text poking Thread-Topic: [PATCH v2 06/20] x86/alternative: use temporary mm for text poking Thread-Index: AQHUt2sRlZaCHhQDiEGNmzE5nFIfqqXRA/aAgAAZ9ACAABHSgIAAWTuA Date: Tue, 5 Feb 2019 17:54:56 +0000 Message-ID: <6D321F51-6B19-46F6-91AC-74248A542BA0@vmware.com> References: <20190129003422.9328-1-rick.p.edgecombe@intel.com> <20190129003422.9328-7-rick.p.edgecombe@intel.com> <20190205095853.GJ21801@zn.tnic> <20190205113146.GP17528@hirez.programming.kicks-ass.net> <20190205123533.GN21801@zn.tnic> In-Reply-To: <20190205123533.GN21801@zn.tnic> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=namit@vmware.com; x-originating-ip: [66.170.99.1] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;BYAPR05MB6296;20:QxqDJfbj9XKfepbpbqVmkv5766jXl1JorpcDc6xl1KJTVSUXIhn8Yppt06+640zAjKe19ZUYjxzlT4M0m9fIzrT19NXajABrJO1ZdDj+E2tBtRdgF4MdWJDksNZuGxoMluWmebwHQGTI/5LvMPDyWX2bkhPN5tJcnu8luW5HTyM= x-ms-office365-filtering-correlation-id: 233f17a2-c471-4c41-7414-08d68b930a6a x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600110)(711020)(4605077)(2017052603328)(7153060)(7193020);SRVR:BYAPR05MB6296; x-ms-traffictypediagnostic: BYAPR05MB6296: x-microsoft-antispam-prvs: x-forefront-prvs: 0939529DE2 x-forefront-antispam-report: SFV:NSPM;SFS:(10009020)(136003)(376002)(366004)(346002)(396003)(39860400002)(189003)(199004)(81156014)(105586002)(81166006)(93886005)(8936002)(106356001)(2906002)(83716004)(7736002)(86362001)(305945005)(66066001)(14454004)(76176011)(33656002)(71190400001)(97736004)(7416002)(8676002)(316002)(186003)(4744005)(54906003)(26005)(71200400001)(6436002)(36756003)(102836004)(446003)(478600001)(6916009)(99286004)(82746002)(476003)(256004)(68736007)(4326008)(6512007)(2616005)(11346002)(6506007)(53546011)(229853002)(6116002)(3846002)(6486002)(53936002)(6246003)(486006)(25786009);DIR:OUT;SFP:1101;SCL:1;SRVR:BYAPR05MB6296;H:BYAPR05MB4776.namprd05.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;MX:1;A:1; received-spf: None (protection.outlook.com: vmware.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: Ul9qel0S4EZTHba0GgO2eznZQaY624VlPUugjgCH3NFi1b4exP8NOmkXrIxJZBzWQ/9PO790babvf+zx0YTNmHw23UGyw+mITeq8dcEnV5+WT1i9k92R332oCrqA6Z8JAnwzltUXeqkJcatAvWsRexKqhuZHdeCsagmB0PBY7TzMef7OAIl8fLzvwsHHguiU5yeqHfAa2iELj+whTRRM1Q8CXeQbWt8QFB9a2cHOmgTFxjVn3xkqKtGVfQMrXAMNpVAtDbObNsQZnoK2nHGtGARUrWZoGqMzAKQbFIxf5JIb1ZR7/HV7NgpPJ9EEmbA7y7Zd4I/poK/y8+sK/8alNNmUlobAlWEwuYz4Sx5l8KKbdDUXjG84E1cep7hBpaKFiBrw/Bwevt7zMPU34CU4iPzUYAUAlTWAJLxE753GYJY= Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: vmware.com X-MS-Exchange-CrossTenant-Network-Message-Id: 233f17a2-c471-4c41-7414-08d68b930a6a X-MS-Exchange-CrossTenant-originalarrivaltime: 05 Feb 2019 17:54:56.8334 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b39138ca-3cee-4b4a-a4d6-cd83d9dd62f0 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR05MB6296 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Feb 5, 2019, at 4:35 AM, Borislav Petkov wrote: >=20 > On Tue, Feb 05, 2019 at 12:31:46PM +0100, Peter Zijlstra wrote: >> ... >>=20 >> So while in general I agree with BUG_ON() being undesirable, I think >> liberal sprinking in text_poke() is fine; you really _REALLY_ want this >> to work or fail loudly. Text corruption is just painful. >=20 > Ok. It would be good to have the gist of this sentiment in a comment > above it so that it is absolutely clear why we're doing it. I added a short comment for v3 above each BUG_ON(). > And since text_poke() can't fail, then it doesn't need a retval too. > AFAICT, nothing is actually using it. As Peter said, this is addressed in a separate patch (one patch per logical change).