From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: [PATCH] tpm: fix buffer overflow in /dev/tpm0 Date: Mon, 12 Sep 2016 10:50:57 +0300 Message-ID: <20160912075057.GA5094@intel.com> References: <1473596340-11376-1-git-send-email-jarkko.sakkinen@linux.intel.com> <20160912040546.GA14625@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20160912040546.GA14625-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tpmdd-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Jason Gunthorpe Cc: "moderated list:TPM DEVICE DRIVER" , open list List-Id: tpmdd-devel@lists.sourceforge.net On Sun, Sep 11, 2016 at 10:05:46PM -0600, Jason Gunthorpe wrote: > On Sun, Sep 11, 2016 at 03:19:00PM +0300, Jarkko Sakkinen wrote: > > tpm_write() does not check whether the buffer has at least enough space > > for the header before passing it to tpm_transmit() so an overflow can > > happen. > > Eh? > > tpm_write uses a hard wired buffer size of TPM_BUFSIZE when working > with tpm_transmit. > > in_size is never used except for the copy. We should probably fix that > to sanity check the header length vs in_size. > > That doesn't seem to be a security issue however because the header > length is propery limited to TPM_BUFSIZE and the data buffer is > allocated specifically for that process using kzalloc. I was working on something else when I bumped into this. The commit message is not the best possible but still the issue is valid although it does not cause any imaginable harm because there is always TPM_BUFSIZE of room in the buffer passed by tpm_write. I'll update the commit message not to speak about tpm_write. "tpm_transmit() does not check whether the bufsiz can contain the TPM header. Add check for this and return -EINVAL if it the buffer is too small." The check should be in tpm_transmit() and also the commit message should be only about that. > Jason /Jarkko ------------------------------------------------------------------------------