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=-0.7 required=3.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 B9C50C10F25 for ; Mon, 9 Mar 2020 19:35:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 983842465A for ; Mon, 9 Mar 2020 19:35:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726403AbgCITfF convert rfc822-to-8bit (ORCPT ); Mon, 9 Mar 2020 15:35:05 -0400 Received: from mail-oln040092068083.outbound.protection.outlook.com ([40.92.68.83]:54531 "EHLO EUR02-HE1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725992AbgCITfF (ORCPT ); Mon, 9 Mar 2020 15:35:05 -0400 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=g3rQAArBPqovEB66sv7k0plhWBS1hQDLOp3nCvw3dSoVEMx+FZgpqxW3wsI0zxQrgPv/IOzSWmRFxslxhUS+nCYY4ro/E5kdq6kI/s4QfdeJzyATkCt8BQYd6KZeNBa9xtO7Gqce5qNEXRDT6PItgUDOMKY3bJY6d+CHs63P2qE6TcUj4KV0zzE3fv+L49SPeJk7xOVFrWTHwqlMmQTK+6lUcjuiLrGuI8mXtH6pc8FXmvfxRdJ3lI+Sex6J5j707Np5NbA5xOxRhzarSBfHSAHV80IuzW9jI0A+YHqgHG5btU7MwHG9+5qVZBfH8oAr3MJf0XUMF20oxUiXJBuQ9A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=TNF+ypRjnXNodGw7+eEn6FxwMgQlbpZjkBUCLzykMlY=; b=IUBTPXhnmfRoEopqrb2jp8hZjUE9JzRHXzOJg7VTN+e26Ftvda3vHP4ypYLiTj1qcsB9ztB0r/OD37wnAJva9Ovs8EbqtJLLwQMOOlG+1EN1XsGSCN41qWt2yI21dsYrAOOs9cBt0YGEp1o8h28aKMoQCMhPTxuqAYJ9ST3bBvuzpp7RWSaYvaw1hePOhktRrp41nU1D+kUwLpHtEsyOCyDG9V1FQcKBENZd8Q+aKbvf7Wq9SfHJTYwQEqU2sYnRQs4U3+Vq4Ubprd6OKU2xDdo9gA9SLJgGxH162eVC8hb7jfGyp41agcc7bedgSTEKFe8g0/7ifSa28BLJVdsfJg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=none; dmarc=none; dkim=none; arc=none Received: from VE1EUR02FT019.eop-EUR02.prod.protection.outlook.com (2a01:111:e400:7e1e::35) by VE1EUR02HT202.eop-EUR02.prod.protection.outlook.com (2a01:111:e400:7e1e::342) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2793.11; Mon, 9 Mar 2020 19:34:59 +0000 Received: from AM6PR03MB5170.eurprd03.prod.outlook.com (10.152.12.60) by VE1EUR02FT019.mail.protection.outlook.com (10.152.12.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2793.11 via Frontend Transport; Mon, 9 Mar 2020 19:34:59 +0000 Received: from AM6PR03MB5170.eurprd03.prod.outlook.com ([fe80::1956:d274:cab3:b4dd]) by AM6PR03MB5170.eurprd03.prod.outlook.com ([fe80::1956:d274:cab3:b4dd%6]) with mapi id 15.20.2772.019; Mon, 9 Mar 2020 19:34:59 +0000 Received: from [192.168.1.101] (92.77.140.102) by AM0PR06CA0072.eurprd06.prod.outlook.com (2603:10a6:208:aa::49) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2793.16 via Frontend Transport; Mon, 9 Mar 2020 19:34:58 +0000 From: Bernd Edlinger To: "Eric W. Biederman" CC: Christian Brauner , Kees Cook , Jann Horn , Jonathan Corbet , Alexander Viro , Andrew Morton , Alexey Dobriyan , Thomas Gleixner , Oleg Nesterov , Frederic Weisbecker , Andrei Vagin , Ingo Molnar , "Peter Zijlstra (Intel)" , Yuyang Du , David Hildenbrand , Sebastian Andrzej Siewior , Anshuman Khandual , David Howells , James Morris , Greg Kroah-Hartman , Shakeel Butt , Jason Gunthorpe , Christian Kellner , Andrea Arcangeli , Aleksa Sarai , "Dmitry V. Levin" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "stable@vger.kernel.org" , "linux-api@vger.kernel.org" Subject: Re: [PATCH v2 4/5] exec: Move exec_mmap right after de_thread in flush_old_exec Thread-Topic: [PATCH v2 4/5] exec: Move exec_mmap right after de_thread in flush_old_exec Thread-Index: AQHV9ZIq8LqSeoOzkk+o9CTpCnOInKhAqHsA Date: Mon, 9 Mar 2020 19:34:59 +0000 Message-ID: References: <87v9nmjulm.fsf@x220.int.ebiederm.org> <202003021531.C77EF10@keescook> <20200303085802.eqn6jbhwxtmz4j2x@wittgenstein> <87v9nlii0b.fsf@x220.int.ebiederm.org> <87a74xi4kz.fsf@x220.int.ebiederm.org> <87r1y8dqqz.fsf@x220.int.ebiederm.org> <87tv32cxmf.fsf_-_@x220.int.ebiederm.org> <87v9ne5y4y.fsf_-_@x220.int.ebiederm.org> <875zfe5xzb.fsf_-_@x220.int.ebiederm.org> In-Reply-To: <875zfe5xzb.fsf_-_@x220.int.ebiederm.org> Accept-Language: en-US, en-GB, de-DE Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: AM0PR06CA0072.eurprd06.prod.outlook.com (2603:10a6:208:aa::49) To AM6PR03MB5170.eurprd03.prod.outlook.com (2603:10a6:20b:ca::23) x-incomingtopheadermarker: OriginalChecksum:79C496411C7C971373B50F97092B52D602659E5707CEC701B2124EABB1337BFE;UpperCasedChecksum:67F7095DB63B9127FCCACBBA6A9CA42499F1591C5E46C3069ADC0B8C0E291EE4;SizeAsReceived:9883;Count:50 x-ms-exchange-messagesentrepresentingtype: 1 x-tmn: [L/99uBRPV/LyRVM1VSZjAibKvfuULYqn] x-microsoft-original-message-id: <4ec7b6c3-da81-bbcd-214f-d12978145288@hotmail.de> x-ms-publictraffictype: Email x-incomingheadercount: 50 x-eopattributedmessage: 0 x-ms-office365-filtering-correlation-id: 159ed0df-750b-4023-81ac-08d7c460f435 x-ms-traffictypediagnostic: VE1EUR02HT202: x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: hdZNzwc6pLT+2ViQ6odqvXNOXUghN906xwKz7gKotZHXwtZ84GBG37ZaQ5MfMRMFX0Bp1hipJLqjJ5vayQGpYGd3co0jNqtL35Ee9UUptvl8j3aws7GjxqJu2rA9COHOUD4HIVWIjmXe6ZCi2MVuGDoLxYMs9Vnfh5uuP0++vgvematv3RWW9vMxUlEEsL1B x-ms-exchange-antispam-messagedata: z84Cpt8/RbEwCJyUJXIKMHrcP50YynlkojBX/rYwVXrlVV7nyCVK+CVnt9b8d+gl19kcMEHMZe/SzH3YeFY7vj4hApKiOoDWjozs3rQJEIy/lYfbXHWd8BPpPUDAhvKhVC1q9NrWzfsCYWqqLePjdQ== x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="Windows-1252" Content-ID: <9E086A324F4FE14290E8EA9DD6C880C2@eurprd03.prod.outlook.com> Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-OriginatorOrg: outlook.com X-MS-Exchange-CrossTenant-RMS-PersistedConsumerOrg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-CrossTenant-Network-Message-Id: 159ed0df-750b-4023-81ac-08d7c460f435 X-MS-Exchange-CrossTenant-rms-persistedconsumerorg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-CrossTenant-originalarrivaltime: 09 Mar 2020 19:34:59.2994 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Internet X-MS-Exchange-CrossTenant-id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa X-MS-Exchange-Transport-CrossTenantHeadersStamped: VE1EUR02HT202 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/8/20 10:38 PM, Eric W. Biederman wrote: > > I have read through the code in exec_mmap and I do not see anything > that depends on sighand or the sighand lock, or on signals in anyway > so this should be safe. > > This rearrangement of code has two siginficant benefits. It makes ^ typo: significant > the determination of passing the point of no return by testing bprm->mm > accurate. All failures prior to that point in flush_old_exec are > either truly recoverable or they are fatal. > > Futher this consolidates all of the possible indefinite waits for ^ typo: Further > userspace together at the top of flush_old_exec. The possible wait > for a ptracer on PTRACE_EVENT_EXIT, the possible wait for a page fault > to be resolved in clear_child_tid, and the possible wait for a page > fault in exit_robust_list. > > This consolidation allows the creation of a mutex to replace > cred_guard_mutex that is not held of possible indefinite userspace can you also reword this "held of" thing here as well? Thanks Bernd.