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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 8DAB9C282CC for ; Mon, 4 Feb 2019 23:24:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 648DB2083B for ; Mon, 4 Feb 2019 23:24:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726480AbfBDXYR (ORCPT ); Mon, 4 Feb 2019 18:24:17 -0500 Received: from mga09.intel.com ([134.134.136.24]:36787 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725900AbfBDXYR (ORCPT ); Mon, 4 Feb 2019 18:24:17 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Feb 2019 15:24:16 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,560,1539673200"; d="scan'208";a="272502853" Received: from baparham-mobl.amr.corp.intel.com (HELO localhost) ([10.249.254.152]) by orsmga004.jf.intel.com with ESMTP; 04 Feb 2019 15:24:12 -0800 Date: Tue, 5 Feb 2019 01:24:11 +0200 From: Jarkko Sakkinen To: "Winkler, Tomas" Cc: "linux-integrity@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "stable@vger.kernel.org" , James Morris , Jerry Snitselaar Subject: Re: [PATCH v2] tpm/tpm_crb: Avoid unaligned reads in crb_recv() Message-ID: <20190204232411.GA14992@linux.intel.com> References: <20190204135943.15756-1-jarkko.sakkinen@linux.intel.com> <5B8DA87D05A7694D9FA63FD143655C1B9DA901F7@hasmsx108.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5B8DA87D05A7694D9FA63FD143655C1B9DA901F7@hasmsx108.ger.corp.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Mon, Feb 04, 2019 at 10:09:51PM +0000, Winkler, Tomas wrote: > > > > The current approach to read first 6 bytes from the response and then tail of > > the response, can cause the 2nd memcpy_fromio() to do an unaligned read > > (e.g. read 32-bit word from address aligned to a 16-bits), depending on how > > memcpy_fromio() is implemented. If this happens, the read will fail and the > > memory controller will fill the read with 1's. > > > > This was triggered by 170d13ca3a2f, which should be probably refined to check > > and react to the address alignment. Before that commit, on x86 > > memcpy_fromio() turned out to be memcpy(). By a luck GCC has done the right > > thing (from tpm_crb's perspective) for us so far, but we should not rely on that. > > Thus, it makes sense to fix this also in tpm_crb, not least because the fix can be > > then backported to stable kernels and make them more robust when compiled > > in differing environments. > > > > Cc: stable@vger.kernel.org > > Cc: James Morris > > Cc: Tomas Winkler > > Cc: Jerry Snitselaar > > Fixes: 30fc8d138e91 ("tpm: TPM 2.0 CRB Interface") > > Signed-off-by: Jarkko Sakkinen > > Reviewed-by: Jerry Snitselaar > After fixing the typos you can add my ack. > Thanks > Tomas > > > --- > > v2: > > * There was a trailing double colon in the end of the short summary. > > * Check requested and expected length against TPM_HEADER_SIZE. > > * Add some explanatory comments to crb_recv(). > > drivers/char/tpm/tpm_crb.c | 22 ++++++++++++++++------ > > 1 file changed, 16 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c index > > 36952ef98f90..c084e61299aa 100644 > > --- a/drivers/char/tpm/tpm_crb.c > > +++ b/drivers/char/tpm/tpm_crb.c > > @@ -287,19 +287,29 @@ static int crb_recv(struct tpm_chip *chip, u8 *buf, > > size_t count) > > struct crb_priv *priv = dev_get_drvdata(&chip->dev); > > unsigned int expected; > > > > - /* sanity check */ > > - if (count < 6) > > + /* A sanity check that the upper layer wants to get at least the header > > + * as that is the minimum size for any TPM response. > > + */ > > + if (count < TPM_HEADER_SIZE) > > return -EIO; > > > > + /* If this bit is set, according to the spec, the TPM is in unrecovable > ^^^ typo ^^^^ > > + * condition. > > + */ > > if (ioread32(&priv->regs_t->ctrl_sts) & CRB_CTRL_STS_ERROR) > > return -EIO; > > > > - memcpy_fromio(buf, priv->rsp, 6); > > - expected = be32_to_cpup((__be32 *) &buf[2]); > > - if (expected > count || expected < 6) > > + /* Read 8 bytes (not just 6 bytes, which would cover ^^^ tag and^^^ the response > > length > > + * field ^^^s^^^) in order to make sure that the reminding memory accesses > ^^^ remaining^^^ > > will > > + * be aligned. > > + */ > > + memcpy_fromio(buf, priv->rsp, 8); > > + > > + expected = be32_to_cpup((__be32 *)&buf[2]); > > + if (expected > count || expected < TPM_HEADER_SIZE) > > return -EIO; > > > > - memcpy_fromio(&buf[6], &priv->rsp[6], expected - 6); > > + memcpy_fromio(&buf[8], &priv->rsp[8], expected - 8); > > > > return expected; > > } > > -- > > 2.19.1 > Thanks! /Jarkko