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From:   Ioana Ciornei <ioana.ciornei@nxp.com>
To:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
CC:     Laurentiu Tudor <laurentiu.tudor@nxp.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "netdev-owner@vger.kernel.org" <netdev-owner@vger.kernel.org>,
        Ioana Ciocoi Radulescu <ruxandra.radulescu@nxp.com>,
        Horia Geanta <horia.geanta@nxp.com>,
        Leo Li <leoyang.li@nxp.com>
Subject: RE: [PATCH v3 2/4] bus: fsl-mc: add fsl-mc userspace support
Thread-Topic: [PATCH v3 2/4] bus: fsl-mc: add fsl-mc userspace support
Thread-Index: AQHUgOdDaPiLexuoCUeDRyxH1kY+eaVY4AQAgAAPQtCAAPNRAIANI/fQ
Date:   Thu, 29 Nov 2018 16:55:35 +0000
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> Subject: Re: [PATCH v3 2/4] bus: fsl-mc: add fsl-mc userspace support
>=20
> On Tue, Nov 20, 2018 at 05:59:26PM +0000, Ioana Ciornei wrote:
> > > > +static int fsl_mc_uapi_send_command(unsigned long arg,
> > > > +				    struct fsl_mc_io *mc_io)
> > > > +{
> > > > +	struct fsl_mc_command mc_cmd;
> > > > +	int error;
> > > > +
> > > > +	error =3D copy_from_user(&mc_cmd, (void __user *)arg, sizeof(mc_c=
md));
> > > > +	if (error)
> > > > +		return -EFAULT;
> > > > +
> > > > +	error =3D mc_send_command(mc_io, &mc_cmd);
> > > > +	if (error)
> > > > +		return error;
> > > > +
> > > > +	error =3D copy_to_user((void __user *)arg, &mc_cmd, sizeof(mc_cmd=
));
> > > > +	if (error)
> > > > +		return -EFAULT;
> > > > +
> > > > +	return 0;
> > > > +}
> > >
> > > I know you said that "the firmware will properly verify the command"
> > > already, but given that I used to be a firmware developer a long
> > > time ago, I can almost guarantee that this will cause problems in the=
 future.
> > >
> > > Want to make a friendly bet about this?
> > >
> > > What is the odds that your firmware api/interface has been properly
> > > fuzzed such that all possible combinations of bad commands will
> > > really not do horrible things to the hardware/system?
> > >
> > > Are you all willing to bet the system intregrity on this?  If so,
> > > ok, it's your systems
> > > :)
> > >
> > > Personally, I think you need to add a "known whitelist" and do some
> > > sort of sanity checking here.
> > >
> >
> > I can add a whitelist on the command ids that can be received from
> > userspace but leave the parameter parsing to the firmware to process
> > and interpret depending on the current system settings.
> >
> > Would that be a viable option from your point of view?
>=20
> That might be a good start.  Again, how well have you tested this firmwar=
e
> interface can handle invalid data?  Are you willing to bet your system in=
tegrity on
> it?  :)
>=20

We understand your concerns regarding the integrity of the MC firmware.

Each command has validation checks inside the MC and we are currently doing=
 extensive testing with fuzzed commands from user space.
We'll come back with a v4 on this once our tests are complete and we are co=
nfident our firmware is robust enough.

Ioana C