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=-3.8 required=3.0 tests=BAYES_00, 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 AB4C9C43465 for ; Sun, 20 Sep 2020 21:13:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7F28420829 for ; Sun, 20 Sep 2020 21:13:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726545AbgITVNq (ORCPT ); Sun, 20 Sep 2020 17:13:46 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:60897 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726503AbgITVNi (ORCPT ); Sun, 20 Sep 2020 17:13:38 -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-64-HkvgTllpM-iYq_Po-gc7vg-1; Sun, 20 Sep 2020 22:13:25 +0100 X-MC-Unique: HkvgTllpM-iYq_Po-gc7vg-1 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; Sun, 20 Sep 2020 22:13:24 +0100 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; Sun, 20 Sep 2020 22:13:24 +0100 From: David Laight To: 'Arnd Bergmann' , Andy Lutomirski CC: Matthew Wilcox , Al Viro , Christoph Hellwig , Andrew Morton , Jens Axboe , David Howells , linux-arm-kernel , X86 ML , LKML , "open list:MIPS" , Parisc List , linuxppc-dev , linux-s390 , sparclinux , linux-block , Linux SCSI List , Linux FS Devel , linux-aio , "io-uring@vger.kernel.org" , linux-arch , Linux-MM , Network Development , "keyrings@vger.kernel.org" , LSM List Subject: RE: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Thread-Topic: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Thread-Index: AQHWj495LxbJUITJXkeWJwtHmAdwxKlyBKsQ Date: Sun, 20 Sep 2020 21:13:24 +0000 Message-ID: <8363d874e503470f8caa201e85e9fbd4@AcuMS.aculab.com> References: <20200918124533.3487701-1-hch@lst.de> <20200918124533.3487701-2-hch@lst.de> <20200920151510.GS32101@casper.infradead.org> <20200920180742.GN3421308@ZenIV.linux.org.uk> <20200920190159.GT32101@casper.infradead.org> <20200920191031.GQ3421308@ZenIV.linux.org.uk> <20200920192259.GU32101@casper.infradead.org> In-Reply-To: Accept-Language: en-GB, 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 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: base64 Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org RnJvbTogQXJuZCBCZXJnbWFubg0KPiBTZW50OiAyMCBTZXB0ZW1iZXIgMjAyMCAyMTo0OQ0KPiAN Cj4gT24gU3VuLCBTZXAgMjAsIDIwMjAgYXQgOToyOCBQTSBBbmR5IEx1dG9taXJza2kgPGx1dG9A a2VybmVsLm9yZz4gd3JvdGU6DQo+ID4gT24gU3VuLCBTZXAgMjAsIDIwMjAgYXQgMTI6MjMgUE0g TWF0dGhldyBXaWxjb3ggPHdpbGx5QGluZnJhZGVhZC5vcmc+IHdyb3RlOg0KPiA+ID4NCj4gPiA+ IE9uIFN1biwgU2VwIDIwLCAyMDIwIGF0IDA4OjEwOjMxUE0gKzAxMDAsIEFsIFZpcm8gd3JvdGU6 DQo+ID4gPiA+IElNTyBpdCdzIG11Y2ggc2FuZXIgdG8gbWFyayB0aG9zZSBhbmQgcmVmdXNlIHRv IHRvdWNoIHRoZW0gZnJvbSBpb191cmluZy4uLg0KPiA+ID4NCj4gPiA+IFNpbXBsZXIgc29sdXRp b24gaXMgdG8gcmVtb3ZlIGlvX3VyaW5nIGZyb20gdGhlIDMyLWJpdCBzeXNjYWxsIGxpc3QuDQo+ ID4gPiBJZiB5b3UncmUgYSAzMi1iaXQgcHJvY2VzcywgeW91IGRvbid0IGdldCB0byB1c2UgaW9f dXJpbmcuICBXb3VsZA0KPiA+ID4gYW55IHJlYWwgdXNlcnMgYWN0dWFsbHkgY2FyZSBhYm91dCB0 aGF0Pw0KPiA+DQo+ID4gV2UgY291bGQgZ28gb25lIHN0ZXAgZmFydGhlciBhbmQgZGVjbGFyZSB0 aGF0IHdlJ3JlIGRvbmUgYWRkaW5nICphbnkqDQo+ID4gbmV3IGNvbXBhdCBzeXNjYWxscyA6KQ0K PiANCj4gV291bGQgeW91IGFsc28gc3RvcCBhZGRpbmcgc3lzdGVtIGNhbGxzIHRvIG5hdGl2ZSAz Mi1iaXQgc3lzdGVtcyB0aGVuPw0KPiANCj4gT24gbWVtb3J5IGNvbnN0cmFpbmVkIHN5c3RlbXMg KGxlc3MgdGhhbiAyR0IgYS50Lm0uKSwgdGhlcmUgaXMgc3RpbGwgYQ0KPiBzdHJvbmcgZGVtYW5k IGZvciBydW5uaW5nIDMyLWJpdCB1c2VyIHNwYWNlLCBidXQgYWxsIG9mIHRoZSByZWNlbnQgQXJt DQo+IGNvcmVzIChhZnRlciBDb3J0ZXgtQTU1KSBkcm9wcGVkIHRoZSBhYmlsaXR5IHRvIHJ1biAz Mi1iaXQga2VybmVscywgc28NCj4gdGhhdCBjb21wYXQgbW9kZSBtYXkgZXZlbnR1YWxseSBiZWNv bWUgdGhlIHByaW1hcnkgd2F5IHRvIHJ1bg0KPiBMaW51eCBvbiBjaGVhcCBlbWJlZGRlZCBzeXN0 ZW1zLg0KPiANCj4gSSBkb24ndCB0aGluayB0aGVyZSBpcyBhbnkgY2hhbmNlIHdlIGNhbiByZWFs aXN0aWNhbGx5IHRha2UgYXdheSBpb191cmluZw0KPiBmcm9tIHRoZSAzMi1iaXQgQUJJIGFueSBt b3JlIG5vdy4NCg0KQ2FuJ3QgaXQganVzdCBydW4gcmVxdWVzdHMgZnJvbSAzMmJpdCBhcHBzIGlu IGEga2VybmVsIHRocmVhZCB0aGF0IGhhcw0KdGhlICdpbl9jb21wYXRfc3lzY2FsbCcgZmxhZyBz ZXQ/DQpOb3QgdGhhdCBpIHJlY2FsbCBzZWVpbmcgdGhlIGNvZGUgd2hlcmUgaXQgc2F2ZXMgdGhl ICdjb21wYXQnIG5hdHVyZQ0Kb2YgYW55IHJlcXVlc3RzLg0KDQpJdCBpcyBhbHJlYWR5IGNvbXBs ZXRlbHkgZipja2VkIGlmIHlvdSB0cnkgdG8gcGFzcyB0aGUgY29tbWFuZCByaW5nDQp0byBhIGNo aWxkIHByb2Nlc3MgLSBpdCB1c2VzIHRoZSB3cm9uZyAnbW0nLg0KSSBzdXNwZWN0IHRoZXJlIGFy ZSBzb21lIHJlYWxseSBob3JyaWQgc2VjdXJpdHkgaG9sZXMgaW4gdGhhdCBhcmVhLg0KDQoJRGF2 aWQuDQoNCi0NClJlZ2lzdGVyZWQgQWRkcmVzcyBMYWtlc2lkZSwgQnJhbWxleSBSb2FkLCBNb3Vu dCBGYXJtLCBNaWx0b24gS2V5bmVzLCBNSzEgMVBULCBVSw0KUmVnaXN0cmF0aW9uIE5vOiAxMzk3 Mzg2IChXYWxlcykNCg== From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Laight Date: Sun, 20 Sep 2020 21:13:24 +0000 Subject: RE: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Message-Id: <8363d874e503470f8caa201e85e9fbd4@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; 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Sun, 20 Sep 2020 22:13:24 +0100 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; Sun, 20 Sep 2020 22:13:24 +0100 From: David Laight To: 'Arnd Bergmann' , Andy Lutomirski Subject: RE: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Thread-Topic: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Thread-Index: AQHWj495LxbJUITJXkeWJwtHmAdwxKlyBKsQ Date: Sun, 20 Sep 2020 21:13:24 +0000 Message-ID: <8363d874e503470f8caa201e85e9fbd4@AcuMS.aculab.com> References: <20200918124533.3487701-1-hch@lst.de> <20200918124533.3487701-2-hch@lst.de> <20200920151510.GS32101@casper.infradead.org> <20200920180742.GN3421308@ZenIV.linux.org.uk> <20200920190159.GT32101@casper.infradead.org> <20200920191031.GQ3421308@ZenIV.linux.org.uk> <20200920192259.GU32101@casper.infradead.org> In-Reply-To: Accept-Language: en-GB, 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 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200920_171340_781034_CDF27981 X-CRM114-Status: GOOD ( 22.22 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-aio , "open list:MIPS" , David Howells , Linux-MM , "keyrings@vger.kernel.org" , sparclinux , Christoph Hellwig , linux-arch , linux-s390 , Linux SCSI List , X86 ML , Matthew Wilcox , linux-block , Al Viro , "io-uring@vger.kernel.org" , linux-arm-kernel , Jens Axboe , Parisc List , Network Development , LKML , LSM List , Linux FS Devel , Andrew Morton , linuxppc-dev Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Arnd Bergmann > Sent: 20 September 2020 21:49 > > On Sun, Sep 20, 2020 at 9:28 PM Andy Lutomirski wrote: > > On Sun, Sep 20, 2020 at 12:23 PM Matthew Wilcox wrote: > > > > > > On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote: > > > > IMO it's much saner to mark those and refuse to touch them from io_uring... > > > > > > Simpler solution is to remove io_uring from the 32-bit syscall list. > > > If you're a 32-bit process, you don't get to use io_uring. Would > > > any real users actually care about that? > > > > We could go one step farther and declare that we're done adding *any* > > new compat syscalls :) > > Would you also stop adding system calls to native 32-bit systems then? > > On memory constrained systems (less than 2GB a.t.m.), there is still a > strong demand for running 32-bit user space, but all of the recent Arm > cores (after Cortex-A55) dropped the ability to run 32-bit kernels, so > that compat mode may eventually become the primary way to run > Linux on cheap embedded systems. > > I don't think there is any chance we can realistically take away io_uring > from the 32-bit ABI any more now. Can't it just run requests from 32bit apps in a kernel thread that has the 'in_compat_syscall' flag set? Not that i recall seeing the code where it saves the 'compat' nature of any requests. It is already completely f*cked if you try to pass the command ring to a child process - it uses the wrong 'mm'. I suspect there are some really horrid security holes in that area. David. - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel