linux-kernel - RE: [PATCH v3] tpm/tpm_crb: Avoid unaligned reads in crb

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Date:   Wed, 6 Feb 2019 12:55:55 +0000
From:   "Winkler, Tomas" <tomas.winkler@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
CC:     "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        Jerry Snitselaar <jsnitsel@...hat.com>
Subject: RE: [PATCH v3] tpm/tpm_crb: Avoid unaligned reads in crb_recv()


 ()
> 
> On Tue, Feb 05, 2019 at 10:57:19PM +0200, Jarkko Sakkinen wrote:
> > On Tue, Feb 05, 2019 at 02:56:02PM +0000, Winkler, Tomas wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: Jarkko Sakkinen [mailto:jarkko.sakkinen@...ux.intel.com]
> > > > Sent: Tuesday, February 05, 2019 16:36
> > > > To: Winkler, Tomas <tomas.winkler@...el.com>
> > > > Cc: linux-integrity@...r.kernel.org; linux-kernel@...r.kernel.org;
> > > > linux- security-module@...r.kernel.org; stable@...r.kernel.org;
> > > > James Morris <jmorris@...ei.org>; Jerry Snitselaar
> > > > <jsnitsel@...hat.com>
> > > > Subject: Re: [PATCH v3] tpm/tpm_crb: Avoid unaligned reads in
> > > > crb_recv()
> > > >
> > > > On Tue, Feb 05, 2019 at 11:07:16AM +0000, Winkler, Tomas wrote:
> > > > > > The current approach to read first 6 bytes from the response
> > > > > > and then tail of the response, can cause the 2nd
> > > > > > memcpy_fromio() to do an unaligned read (e.g. read 32-bit word
> > > > > > from address aligned to a 16-bits), depending on how
> > > > > > memcpy_fromio() is implemented. If this happens, the read will
> > > > > > fail and the memory controller will fill the read with 1's.
> > > > > >
> > > > > > This was triggered by 170d13ca3a2f, which should be probably
> > > > > > refined to check and react to the address alignment. Before
> > > > > > that commit, on
> > > > > > x86
> > > > > > memcpy_fromio() turned out to be memcpy(). By a luck GCC has
> > > > > > done the right thing (from tpm_crb's perspective) for us so
> > > > > > far, but we should not
> > > > rely on that.
> > > > > > Thus, it makes sense to fix this also in tpm_crb, not least
> > > > > > because the fix can be then backported to stable kernels and
> > > > > > make them more robust when compiled in differing environments.
> > > > > >
> > > > > > Cc: stable@...r.kernel.org
> > > > > > Cc: James Morris <jmorris@...ei.org>
> > > > > > Cc: Tomas Winkler <tomas.winkler@...el.com>
> > > > > > Cc: Jerry Snitselaar <jsnitsel@...hat.com>
> > > > > > Fixes: 30fc8d138e91 ("tpm: TPM 2.0 CRB Interface")
> > > > > > Signed-off-by: Jarkko Sakkinen
> > > > > > <jarkko.sakkinen@...ux.intel.com>
> > > > > > Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>
> > > > > > ---
> > > > > > v3:
> > > > > > * Fix typo i.e. %s/reminding/remaining/g
> > > > >
> > > > > Why you haven't fixed all the typos I've pointed out? I think you missed
> that.
> > > >
> > > > I saw only comment about remaining. Was there something else? Can fix.
> > >
> > > https://www.spinics.net/lists/stable/msg283648.html
> > >
> > > 1. unrecovable -> unrecoverable
> > > 2. /* Read 8 bytes (not just 6 bytes, which would cover the tag and
> > > the response  length
> > > > +	 * fields) in order to make sure that the remaining memory
> > > > +accesses */
> >
> > Thanks and apologies for missing these.
> 
> Fixed comments and applied the patch, thank you. Do I amend your acked-by?

Please, do.
Thanks
Tomas