linux-kernel - Re: [PATCH] tpm: fix buffer overflow in /dev/tpm0

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Date:   Sun, 11 Sep 2016 22:05:46 -0600
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        "moderated list:TPM DEVICE DRIVER" 
        <tpmdd-devel@...ts.sourceforge.net>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: fix buffer overflow in /dev/tpm0

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.

Jason