linux-kernel - Re: [kernel-hardening] [PATCH 3/4] Make static usermode helper binaries constant

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Message-ID: <20161214205444.GA16183@kroah.com>
Date:   Wed, 14 Dec 2016 12:54:44 -0800
From:   Greg KH <greg@...ah.com>
To:     kernel-hardening@...ts.openwall.com
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [kernel-hardening] [PATCH 3/4] Make static usermode helper
 binaries constant

On Wed, Dec 14, 2016 at 03:29:52PM -0500, Rich Felker wrote:
> On Wed, Dec 14, 2016 at 10:50:52AM -0800, Greg KH wrote:
> > 
> > There are a number of usermode helper binaries that are "hard coded" in
> > the kernel today, so mark them as "const" to make it harder for someone
> > to change where the variables point to.
> 
> You're not preventing change of where they point to, but rather
> preventing modification of the pointed-to data through these
> pointers...
> 
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > ---
> >  drivers/macintosh/windfarm_core.c          | 2 +-
> >  drivers/net/hamradio/baycom_epp.c          | 2 +-
> >  drivers/pnp/pnpbios/core.c                 | 5 +++--
> >  drivers/staging/greybus/svc_watchdog.c     | 4 ++--
> >  drivers/staging/rtl8192e/rtl8192e/rtl_dm.c | 6 +++---
> >  fs/nfsd/nfs4layouts.c                      | 6 ++++--
> >  security/keys/request_key.c                | 7 ++++---
> >  7 files changed, 18 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/macintosh/windfarm_core.c b/drivers/macintosh/windfarm_core.c
> > index 465d770ab0bb..1b317cbb73cf 100644
> > --- a/drivers/macintosh/windfarm_core.c
> > +++ b/drivers/macintosh/windfarm_core.c
> > @@ -74,7 +74,7 @@ static inline void wf_notify(int event, void *param)
> >  
> >  static int wf_critical_overtemp(void)
> >  {
> > -	static char * critical_overtemp_path = "/sbin/critical_overtemp";
> > +	static const char * critical_overtemp_path = "/sbin/critical_overtemp";
> 
> Should be static char *const critical_overtemp_path, or if you prefer
> static const char *const critical_overtemp_path (since the pointed-to
> data is not modifiable either). Likewise elsewhere.

argh, ok, I failed here, thanks for that, that's what I get for writing
code on an airplane...

let me rework this, I also want to make argv and env static too, just
for good measure.

thanks,

greg k-h