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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 8985FC28CC2 for ; Wed, 29 May 2019 13:51:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6D07722CD8 for ; Wed, 29 May 2019 13:51:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727513AbfE2Nvb convert rfc822-to-8bit (ORCPT ); Wed, 29 May 2019 09:51:31 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:50105 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727086AbfE2Nv2 (ORCPT ); Wed, 29 May 2019 09:51:28 -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-141-3F-5HhagN6e9tnQVnk1CeQ-1; Wed, 29 May 2019 14:51:25 +0100 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; Wed, 29 May 2019 14:51:24 +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; Wed, 29 May 2019 14:51:24 +0100 From: David Laight To: 'Neil Horman' , "linux-kernel@vger.kernel.org" CC: Steve Grubb , Theodore Ts'o , "Arnd Bergmann" , Greg Kroah-Hartman Subject: RE: [PATCH] Fix xoring of arch_get_random_long into crng->state array Thread-Topic: [PATCH] Fix xoring of arch_get_random_long into crng->state array Thread-Index: AQHVFiSGW6uE5jAIekyknyRep1UK46aCHqcQ Date: Wed, 29 May 2019 13:51:24 +0000 Message-ID: References: <20190402220025.14499-1-nhorman@tuxdriver.com> <20190529134200.GA31099@hmswarspite.think-freely.org> In-Reply-To: <20190529134200.GA31099@hmswarspite.think-freely.org> 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: 3F-5HhagN6e9tnQVnk1CeQ-1 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: Neil Horman > Sent: 29 May 2019 14:42 > On Tue, Apr 02, 2019 at 06:00:25PM -0400, Neil Horman wrote: > > When _crng_extract is called, any arch that has a registered > > arch_get_random_long method, attempts to mix an unsigned long value into > > the crng->state buffer, it only mixes in 32 of the 64 bits available, > > because the state buffer is an array of u32 values, even though 2 u32 > > are expected to be filled (owing to the fact that it expects indexes 14 > > and 15 to be filled). > > > > Bring the expected behavior into alignment by casting index 14 to an > > unsignled long pointer, and xoring that in instead. ... > > diff --git a/drivers/char/random.c b/drivers/char/random.c > > index 38c6d1af6d1c..8178618458ac 100644 > > --- a/drivers/char/random.c > > +++ b/drivers/char/random.c > > @@ -975,14 +975,16 @@ static void _extract_crng(struct crng_state *crng, > > __u8 out[CHACHA_BLOCK_SIZE]) > > { > > unsigned long v, flags; > > - > > + unsigned long *archrnd; > > if (crng_ready() && > > (time_after(crng_global_init_time, crng->init_time) || > > time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL))) > > crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL); > > spin_lock_irqsave(&crng->lock, flags); > > - if (arch_get_random_long(&v)) > > - crng->state[14] ^= v; > > + if (arch_get_random_long(&v)) { > > + archrnd = (unsigned long *)&crng->state[14]; > > + *archrnd ^= v; > > + } Isn't that likely to generate a misaligned memory access? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)