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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6675C433EF for ; Sat, 6 Nov 2021 14:13:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89E7960F9D for ; Sat, 6 Nov 2021 14:13:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233582AbhKFOQd (ORCPT ); Sat, 6 Nov 2021 10:16:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229932AbhKFOQd (ORCPT ); Sat, 6 Nov 2021 10:16:33 -0400 Received: from kadath.azazel.net (kadath.azazel.net [IPv6:2001:8b0:135f:bcd1:e0cb:4eff:fedf:e608]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1FDEBC061570 for ; Sat, 6 Nov 2021 07:13:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=azazel.net; s=20190108; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=ybVUpTOEimRbGi0r2y+/yCYBqAdnIxyDWLtyjX3N5cI=; b=tYY9hNfY5wdaUsCPHabruGx1Go 25cj0rVrxI/H46sW75Nl31VUkNWbiaJqOXImfHUwIMdJUxLgFqw0tCvR6FCgyrc81hc2XI9FW7n0y Z5Ha7JmpMH+kqcH40lsbPhKb4TlSsRDUClNzZiJixxMeBfGc2c2MbdnnUezTZyiMWhwb+9d78iqdm JGY3Gnw1f9EgGoUXgPhcmNiQLgH7NbDe7NqiG2pUqCyyFwkGzruRo216SDzRgqw4Zglo7z0wz+Mf6 KCg1RDnIpfSpn/M54nLLgsOPZEclZtSBDE8oN/3RKTLzPuDf45IDbX/fgwaigpQTlnk/6OhDdNDWB jb2hwptw==; Received: from ec2-18-200-185-153.eu-west-1.compute.amazonaws.com ([18.200.185.153] helo=azazel.net) by kadath.azazel.net with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mjMS3-004ja3-U5; Sat, 06 Nov 2021 14:13:48 +0000 Date: Sat, 6 Nov 2021 14:13:43 +0000 From: Jeremy Sowden To: Jan Engelhardt Cc: Netfilter Devel Subject: Re: [ulogd2 PATCH 15/26] input: UNIXSOCK: prevent unaligned pointer access. Message-ID: References: <20211030164432.1140896-1-jeremy@azazel.net> <20211030164432.1140896-16-jeremy@azazel.net> <5op325n6-6077-p0n2-r33o-npr9905n47s3@vanv.qr> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="1cmxNxUMxEsIsR/W" Content-Disposition: inline In-Reply-To: <5op325n6-6077-p0n2-r33o-npr9905n47s3@vanv.qr> X-SA-Exim-Connect-IP: 18.200.185.153 X-SA-Exim-Mail-From: jeremy@azazel.net X-SA-Exim-Scanned: No (on kadath.azazel.net); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org --1cmxNxUMxEsIsR/W Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On 2021-10-30, at 19:42:25 +0200, Jan Engelhardt wrote: > On Saturday 2021-10-30 18:44, Jeremy Sowden wrote: > >`struct ulogd_unixsock_packet_t` is packed, so taking the address of its > >`struct iphdr payload` member may yield an unaligned pointer value. > > That may not be a problem. Dereferencing through a pointer to > a packed struct generates very pessimistic code even when there is no > padding internally: Having taken another look at this, I've adopted different approach to pacify the compiler: the pointer is only actually dereferenced to read one member (`ip->version`), so I shall replace the local pointer variable with an `ip_version` variable instead. J. --1cmxNxUMxEsIsR/W Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEbB20U2PvQDe9VtUXKYasCr3xBA0FAmGGjZcACgkQKYasCr3x BA1guhAAyuF/Fs7cH4/Hq8qbIz/rDuc/0PedxFnbTU+31qBuFQaXx113VSNdbvp6 V5dU5+fXV8ShTE397/H5KAfqEsDX5YC7hdPCU53aG/BpAKWdCZbxNyaWuVuiUH8j +mNcEDOlWpRaiRanTB05fSqsRhhOuWkRM72F9S8GcwXErbP7iCmqTdb2/Eh2zRfy +hZOGodfxmtRfqris32uph0g9TXXodJi9ePGAZuUAADirb9zwU9ODDZLtaLlCd/I v+3sERU9zBdH1ZPllfGexah2GWYIZIE5UHFnYrD7w2OU1TuwQqZkeIIznQ5AGVw/ TogT84jv3FU13h0ldI6f6E/y5/SeWFzNIY7LZntehJq0Oug7wTHB41XPk+yw2jY4 jF0+n87zMd9nrMwLzlzwFbmEvnIHeOFlwNL5BVKZf4pRg85CLdT2nvRbXd5mjBUX MjENkiS5IZ8gV7U2iPlt2Y120JXh3m3nXO1K6ABDL0jGRx0UujKhrE2+Oo1tXE0i XTLhJffx/OGgsW0ZEhvmu5yHDTti9bRhFWY6/FsVjGbvG6eeECpsGI1hM0MMrF71 kIckLgx8FhL3gcMcc+M75OubyoG54LXWtanKimfFkHaIWOUTFGuKEaMfO+pGYh2x e0uiQwX+RdJKyQZ0WXqh1OZyUT+CNQoEYpTmJG3d0Xvp3TUggzs= =bLu7 -----END PGP SIGNATURE----- --1cmxNxUMxEsIsR/W--