Re: [PATCH] tpm: Add module parameter for hwrng quality.

Jason Gunthorpe
2018-06-18T19:33:16Z

On Mon, Jun 18, 2018 at 09:07:12PM +0300, Jarkko Sakkinen wrote:
> On Fri, Jun 08, 2018 at 02:54:38PM +0800, Louis Collard wrote:
> > It is now possible for drivers to easily specify a hwrng quality, however
> > most do not currently do this, and in cases where they do, it may be
> > desirable to override the driver-specified value with a user-specified
> > one. This patch adds a parameter to set or override the hwrng quality.
> >
> > Signed-off-by: Louis Collard <louiscollard@chromium.org>
> > drivers/char/tpm/tpm-chip.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index 0a62c19937b6..4def49cfc634 100644
> > +++ b/drivers/char/tpm/tpm-chip.c
> > @@ -33,6 +33,11 @@
> > DEFINE_IDR(dev_nums_idr);
> > static DEFINE_MUTEX(idr_lock);
> >
> > +static short override_rng_quality = -1;
> > +module_param(override_rng_quality, short, 0644);
>
> Should this be 600 i.e. not to leak this information?

There is a real push these days against adding module parameters, and
apparently, IMA can't function with TPM as a module.

Are you sure this shouldn't be done in some other way?

Jason