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 E7A53C388F7 for ; Thu, 5 Nov 2020 09:00:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 99A102068D for ; Thu, 5 Nov 2020 09:00:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730542AbgKEJAG convert rfc822-to-8bit (ORCPT ); Thu, 5 Nov 2020 04:00:06 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:47325 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729263AbgKEJAG (ORCPT ); Thu, 5 Nov 2020 04:00:06 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-231-8UX6HNYcNJS69Go7Z9G_5w-1; Thu, 05 Nov 2020 09:00:01 +0000 X-MC-Unique: 8UX6HNYcNJS69Go7Z9G_5w-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; Thu, 5 Nov 2020 09:00:00 +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, 5 Nov 2020 09:00:00 +0000 From: David Laight To: 'Daniel Xu' , "bpf@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "ast@kernel.org" , "daniel@iogearbox.net" CC: "kernel-team@fb.com" Subject: RE: [PATCH bpf v2 1/2] lib/strncpy_from_user.c: Don't overcopy bytes after NUL terminator Thread-Topic: [PATCH bpf v2 1/2] lib/strncpy_from_user.c: Don't overcopy bytes after NUL terminator Thread-Index: AQHWsxsIE6fPG3mijk+FzhsUr3fzDam5OvTg Date: Thu, 5 Nov 2020 09:00:00 +0000 Message-ID: References: <487a07aa911b4e822a0b931f7b33a4f67fedb6bd.1604542786.git.dxu@dxuuu.xyz> In-Reply-To: <487a07aa911b4e822a0b931f7b33a4f67fedb6bd.1604542786.git.dxu@dxuuu.xyz> 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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Xu > Sent: 05 November 2020 02:26 ... > --- a/lib/strncpy_from_user.c > +++ b/lib/strncpy_from_user.c > @@ -35,17 +35,22 @@ static inline long do_strncpy_from_user(char *dst, const char __user *src, > goto byte_at_a_time; > > while (max >= sizeof(unsigned long)) { > - unsigned long c, data; > + unsigned long c, data, mask, *out; > > /* Fall back to byte-at-a-time if we get a page fault */ > unsafe_get_user(c, (unsigned long __user *)(src+res), byte_at_a_time); It's not related to this change, but since both addresses are aligned (checked earlier) a page fault on the word read is fatal. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)