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

Greg KH
2016-12-14T20:54:36Z

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@linuxfoundation.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