From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: [PATCH v3] tpm-dev-common: Reject too short writes Date: Sat, 9 Sep 2017 15:53:47 +0300 Message-ID: <20170909125347.y3zgvpnbdywqxi54@linux.intel.com> References: <20170908152132.8728-1-Alexander.Steffen@infineon.com> <20170908213739.k7ifm2isz4dciaaa@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170908213739.k7ifm2isz4dciaaa@linux.intel.com> Sender: stable-owner@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 Sat, Sep 09, 2017 at 12:37:39AM +0300, Jarkko Sakkinen wrote: > On Fri, Sep 08, 2017 at 05:21:32PM +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. > > v3: > > - Access data copied from user space (priv->data_buffer) instead of user > > space data directly (buf). > > - Changed return code to EINVAL. > > > > drivers/char/tpm/tpm-dev-common.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c > > index 610638a..461bf0b 100644 > > --- a/drivers/char/tpm/tpm-dev-common.c > > +++ b/drivers/char/tpm/tpm-dev-common.c > > @@ -110,6 +110,12 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf, > > return -EFAULT; > > } > > > > + if (in_size < 6 || > > + in_size < be32_to_cpu(*((__be32 *) (priv->data_buffer + 2)))) { > > + mutex_unlock(&priv->buffer_mutex); > > + return -EINVAL; > > + } > > + > > /* atomic tpm command send and result receive. We only hold the ops > > * lock during this period so that the tpm can be unregistered even if > > * the char dev is held open. > > -- > > 2.7.4 > > > > I'm not gonna fight about that "in_size < 6" check. I think it is not > needed, I understand your point but still disagree but it is something > where I can live with having it. > > I kind of disagree also with allowing messages longer than the command > size but it does not have to be in the scope of this commit and actually > should be a separate discussion if we ever going to do something about > it. > > Thanks for the patience! > > Reviewed-by: Jarkko Sakkinen > > /Jarkko Without your fix: $ python -m unittest -v tpm2_smoke.SmokeTest.test_too_short_cmd test_too_short_cmd (tpm2_smoke.SmokeTest) ... FAIL ====================================================================== FAIL: test_too_short_cmd (tpm2_smoke.SmokeTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "tpm2_smoke.py", line 157, in test_too_short_cmd self.assertEqual(rejected, True) AssertionError: False != True ---------------------------------------------------------------------- Ran 1 test in 2.108s FAILED (failures=1) The test case expects to get a posix error, which it doesn't get. With your fix: $ python -m unittest -v tpm2_smoke.SmokeTest.test_too_short_cmd test_too_short_cmd (tpm2_smoke.SmokeTest) ... ok ---------------------------------------------------------------------- Ran 1 test in 2.099s OK So looks good to me. Tested-by: Jarkko Sakkinen Can you test the master branch with SPI TPM? I had to tinker your commits a bit because of merge conflicts with Arnd's commit. I'll put everything back to next as soon as I hear from you. Thanks /Jarkko