From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: [PATCH v2] tpm-dev-common: Reject too short writes Date: Wed, 6 Sep 2017 15:50:33 +0300 Message-ID: <20170906125033.32cwy27inzecfo3i@linux.intel.com> References: <20170904173642.5988-1-Alexander.Steffen@infineon.com> <20170906124233.qquzut5lyuri2buu@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170906124233.qquzut5lyuri2buu@linux.intel.com> Sender: owner-linux-security-module@vger.kernel.org To: Alexander Steffen Cc: tpmdd-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, stable@vger.kernel.org List-Id: tpmdd-devel@lists.sourceforge.net On Wed, Sep 06, 2017 at 03:42:33PM +0300, Jarkko Sakkinen wrote: > On Mon, Sep 04, 2017 at 07:36:42PM +0200, Alexander Steffen wrote: > > tpm_transmit() does not offer an explicit interface to indicate the number > > of valid bytes in the communication buffer. Instead, it relies on the > > commandSize field in the TPM header that is encoded within the buffer. > > Therefore, ensure that a) enough data has been written to the buffer, so > > that the commandSize field is present and b) the commandSize field does not > > announce more data than has been written to the buffer. > > > > This should have been fixed with CVE-2011-1161 long ago, but apparently > > a correct version of that patch never made it into the kernel. > > > > Cc: stable@vger.kernel.org > > Signed-off-by: Alexander Steffen > > --- > > v2: > > - Moved all changes to tpm_common_write in a single patch. > > > > drivers/char/tpm/tpm-dev-common.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c > > index 610638a..ac25574 100644 > > --- a/drivers/char/tpm/tpm-dev-common.c > > +++ b/drivers/char/tpm/tpm-dev-common.c > > @@ -99,7 +99,8 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf, > > if (atomic_read(&priv->data_pending) != 0) > > return -EBUSY; > > > > - if (in_size > TPM_BUFSIZE) > > + if (in_size > sizeof(priv->data_buffer) || in_size < 6 || > > + in_size < be32_to_cpu(*((__be32 *) (buf + 2)))) > > return -E2BIG; > > > > mutex_lock(&priv->buffer_mutex); > > -- > > 2.7.4 > > > > How did you test this change after you implemented it? > > Just thinking what to add to https://github.com/jsakkine-intel/tpm2-scripts > > /Jarkko Just when I started to implement this that the bug fix itself does not have yet the right semantics. It should be just add a new check: if (in_size != be32_to_cpu(*((__be32 *) (buf + 2)))) return -EINVAL; The existing check is correct. This was missing. The reason for this is that we process whatever is in the in_size bytes as a full command. Sorry I didn't notice before I started to implement a test case. /Jarkko