From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Alexander Steffen <Alexander.Steffen@infineon.com>
Cc: tpmdd-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v2] tpm-dev-common: Reject too short writes
Date: Wed, 6 Sep 2017 15:50:33 +0300 [thread overview]
Message-ID: <20170906125033.32cwy27inzecfo3i@linux.intel.com> (raw)
In-Reply-To: <20170906124233.qquzut5lyuri2buu@linux.intel.com>
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 <Alexander.Steffen@infineon.com>
> > ---
> > 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
next prev parent reply other threads:[~2017-09-06 12:50 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-04 17:36 [PATCH v2] tpm-dev-common: Reject too short writes Alexander Steffen
2017-09-05 19:05 ` Jarkko Sakkinen
2017-09-06 12:42 ` Jarkko Sakkinen
2017-09-06 12:50 ` Jarkko Sakkinen [this message]
2017-09-06 14:19 ` Alexander.Steffen
2017-09-07 16:46 ` Jarkko Sakkinen
2017-09-08 14:26 ` Alexander.Steffen
2017-09-08 21:34 ` Jarkko Sakkinen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170906125033.32cwy27inzecfo3i@linux.intel.com \
--to=jarkko.sakkinen@linux.intel.com \
--cc=Alexander.Steffen@infineon.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=stable@vger.kernel.org \
--cc=tpmdd-devel@lists.sourceforge.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).