linux-kernel - Re: Change CONFIG_DEVKMEM default value to n

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Date:   Mon, 10 Oct 2016 10:44:36 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>, Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: Re: Change CONFIG_DEVKMEM default value to n

On 10/07/16 at 05:57am, Greg Kroah-Hartman wrote:
> On Fri, Oct 07, 2016 at 10:04:11AM +0800, Dave Young wrote:
> > Kconfig comment suggests setting it as "n" if in doubt thus move the
> > default value to 'n'.
> > 
> > Signed-off-by: Dave Young <dyoung@...hat.com>
> > Suggested-by: Kees Cook <keescook@...omium.org>
> > ---
> >  drivers/char/Kconfig |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > --- linux-x86.orig/drivers/char/Kconfig
> > +++ linux-x86/drivers/char/Kconfig
> > @@ -17,7 +17,7 @@ config DEVMEM
> >  
> >  config DEVKMEM
> >  	bool "/dev/kmem virtual device support"
> > -	default y
> > +	default n
> 
> If you remove the "default" line, it defaults to 'n'.

I personally perfer a "default n", but I can update it..

> 
> And is it really "safe" to default this to n now?

There is an old article here:
https://lwn.net/Articles/147901/

AFAIK Distributions like Fedora/Debian has disabled it for long time.
If one really need it he can still enable it in his own config file.

> 
> thanks,
> 
> greg k-h

Thanks
Dave