Vaio eeprom security issue

Greg KH greg at kroah.com
Tue Aug 12 00:08:06 CEST 2003


On Mon, Aug 11, 2003 at 11:46:29PM +0200, Jean Delvare wrote:
> 
> > > Not really. Looks complicated ;) and it seems these are capabilities
> > > you give to a user/process, not to a file. I just don't want to dive
> > > into this for something that "simple".
> > 
> > Why?  Just check for CAP_SYS_ADMIN if the Vaio is detected.  If that
> > succeeds, then give access, otherwise deny it.
> 
> I'm not sure I understand how it works. Whose capabilities are checked?
> The person accessing the proc file?

Yes.

> In this case, yes, it would make sense. I would then have something
> like:
> 
> if (!capable(CAP_SYS_ADMIN)) {
> 	/* show the real data */
> } else {
> 	/* show zeroes only */
> }
> 
> Is that it?

Looks good to me, as long as you have done the check for Vaio previous
to this.

> I don't know actually what I should display for non-root users

0 looks like a good choice.

> (btw, CAP_SYS_ADMIN == root, or is it more complex?).

It's a bit more complex.  You can allow some users some rights.
Traditionally root gets them all, but you can revoke some of them for
some instances of root.  In reality, it's not used that much :(

For a much more complex version of something like this, with different
rights for different users, take a look at the SELinux stuff which just
got merged into the 2.6.0-test3 kernel.  It uses the LSM framework to
catch all of this kind of stuff (LSM hooks into the capability call.)
But this is off-topic for sensors, sorry...

> > > Remember, the eeprom module, although widely used, is one of our
> > > least interesting drivers.
> > 
> > But it's fun to play with :)
> 
> Sure it is, that's the one I started with (due to that Vaio EEPROM
> already). But it's also one of the slowest drivers, and I believe we'll
> get rid of it someday (I really plan not to load it by default at some
> time).

I have a port of it in my 2.6 tree, that I need to move over to the
binary sysfs file interface before adding.  It's so simple I use it for
testing all the time.

> > > And LM Sensors is useless on Sony Vaio's anyway (no sensor chips).
> > 
> > Looks like the eeprom driver works :)
> 
> Yes it does, but do users install lm_sensors to read how many memory
> they do have in their laptop? I doubt it.

Who knows :)

> > > So let's play it safe, but without extra technologies involved. Do
> > > not export the eeproms detected as Vaio's ones unless forced too.
> > 
> > What does "forced too" mean here?
> 
> Force like in "modprobe eeprom force=0,0x57".

Ah.  Makes sense.

thanks,

greg k-h



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