Re: [PATCH] clk: Emit a stern warning with writable debugfs enabled

[Stephen Boyd <sboyd@kernel.org>]

Quoting Geert Uytterhoeven (2021-12-09 23:57:25)
> Hi Stephen,
> 
> On Fri, Dec 10, 2021 at 2:42 AM Stephen Boyd <sboyd@kernel.org> wrote:
> > We don't want vendors to be enabling this part of the clk code and
> > shipping it to customers. Exposing the ability to change clk frequencies
> > and parents via debugfs is potentially damaging to the system if folks
> > don't know what they're doing. Emit a strong warning so that the message
> > is clear: don't enable this outside of development systems.
> >
> > Fixes: 37215da5553e ("clk: Add support for setting clk_rate via debugfs")
> > Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> > Signed-off-by: Stephen Boyd <sboyd@kernel.org>
> 
> Thanks for your patch!
> 
> > --- a/drivers/clk/clk.c
> > +++ b/drivers/clk/clk.c
> > @@ -3383,6 +3383,24 @@ static int __init clk_debug_init(void)
> >  {
> >         struct clk_core *core;
> >
> > +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> > +       pr_warn("\n");
> > +       pr_warn("********************************************************************\n");
> > +       pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE           **\n");
> > +       pr_warn("**                                                                **\n");
> > +       pr_warn("**  WRITEABLE clk DebugFS SUPPORT HAS BEEN ENABLED IN THIS KERNEL **\n");
> > +       pr_warn("**                                                                **\n");
> > +       pr_warn("** This means that this kernel is built to expose clk operations  **\n");
> > +       pr_warn("** such as parent or rate setting, enabling, disabling, etc.      **\n");
> > +       pr_warn("** to userspace, which may compromise security on your system.    **\n");
> > +       pr_warn("**                                                                **\n");
> > +       pr_warn("** If you see this message and you are not debugging the          **\n");
> > +       pr_warn("** kernel, report this immediately to your vendor!                **\n");
> > +       pr_warn("**                                                                **\n");
> > +       pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE           **\n");
> > +       pr_warn("********************************************************************\n");
> 
> So how many variants of such blocks do we have now in the kernel?
> 

Quite a few!