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[72.223.3.97]) by smtp.gmail.com with ESMTPSA id o21sm7689506qto.18.2019.02.01.10.42.15 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 01 Feb 2019 10:42:16 -0800 (PST) Date: Fri, 1 Feb 2019 11:42:14 -0700 From: Jerry Snitselaar To: Jarkko Sakkinen Cc: linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, stable@vger.kernel.org, Linus Torvalds , James Morris , Tomas Winkler Subject: Re: [PATCH] tpm/tpm_crb: Avoid unaligned reads in crb_recv(): Message-ID: <20190201184214.aohoxqu7cyngehqk@cantor> Reply-To: Jerry Snitselaar Mail-Followup-To: Jarkko Sakkinen , linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, stable@vger.kernel.org, Linus Torvalds , James Morris , Tomas Winkler References: <20190201111949.14881-1-jarkko.sakkinen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190201111949.14881-1-jarkko.sakkinen@linux.intel.com> User-Agent: NeoMutt/20180716 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri Feb 01 19, Jarkko Sakkinen 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: Linus Torvalds >Cc: James Morris >Cc: Tomas Winkler >Cc: Jerry Snitselaar >Fixes: 30fc8d138e91 ("tpm: TPM 2.0 CRB Interface") >Signed-off-by: Jarkko Sakkinen >--- > drivers/char/tpm/tpm_crb.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > >diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c >index 36952ef98f90..7f47e43aa9f1 100644 >--- a/drivers/char/tpm/tpm_crb.c >+++ b/drivers/char/tpm/tpm_crb.c >@@ -288,18 +288,18 @@ static int crb_recv(struct tpm_chip *chip, u8 *buf, size_t count) > unsigned int expected; > > /* sanity check */ >- if (count < 6) >+ if (count < 8) > return -EIO; > > if (ioread32(&priv->regs_t->ctrl_sts) & CRB_CTRL_STS_ERROR) > return -EIO; > >- memcpy_fromio(buf, priv->rsp, 6); >+ memcpy_fromio(buf, priv->rsp, 8); > expected = be32_to_cpup((__be32 *) &buf[2]); >- if (expected > count || expected < 6) >+ if (expected > count || expected < 8) > return -EIO; > >- memcpy_fromio(&buf[6], &priv->rsp[6], expected - 6); >+ memcpy_fromio(&buf[8], &priv->rsp[8], expected - 8); > > return expected; > } >-- >2.17.1 > Reviewed-by: Jerry Snitselaar