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[209.132.180.67]) by mx.google.com with ESMTP id u11si4334110edi.385.2019.10.31.04.41.57; Thu, 31 Oct 2019 04:42:19 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726734AbfJaLlL convert rfc822-to-8bit (ORCPT + 99 others); Thu, 31 Oct 2019 07:41:11 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:51684 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726713AbfJaLlL (ORCPT ); Thu, 31 Oct 2019 07:41:11 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-109-GB0xbnyiMwuYT7SsYZLvhA-2; Thu, 31 Oct 2019 11:41:06 +0000 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Thu, 31 Oct 2019 11:41:06 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Thu, 31 Oct 2019 11:41:06 +0000 From: David Laight To: 'Christian Brauner' , "linux-kernel@vger.kernel.org" , Florian Weimer , GNU C Library CC: Arnd Bergmann , Kees Cook , "Jann Horn" , David Howells , Ingo Molnar , Oleg Nesterov , Linus Torvalds , Peter Zijlstra , "linux-api@vger.kernel.org" , "stable@vger.kernel.org" Subject: RE: [PATCH] clone3: validate stack arguments Thread-Topic: [PATCH] clone3: validate stack arguments Thread-Index: AQHVj99vS5K32QXnq0iIRbo0zlqhOad0n6Aw Date: Thu, 31 Oct 2019 11:41:06 +0000 Message-ID: References: <20191031113608.20713-1-christian.brauner@ubuntu.com> In-Reply-To: <20191031113608.20713-1-christian.brauner@ubuntu.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: GB0xbnyiMwuYT7SsYZLvhA-2 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Christian Brauner > Sent: 31 October 2019 11:36 ... > /* Intentional user visible API change */ > clone3() was released with 5.3. Currently, it is not documented and very > unclear to userspace how the stack and stack_size argument have to be > passed. After talking to glibc folks we concluded that trying to change > clone3() to setup the stack instead of requiring userspace to do this is > the right course of action. What happens if someone 'accidentally' runs a program compiled for the new API on a system running the existing 5.3 kernel? While it won't work, it needs to die reasonably gracefully. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)