Re: exported symbols

[Greg KH <greg@kroah.com>]

On Sun, Sep 20, 2009 at 07:21:36AM +0200, Julia Lawall wrote:
> On Sat, 19 Sep 2009, Greg KH wrote:
> 
> > On Fri, Sep 18, 2009 at 11:39:34PM +0200, Julia Lawall wrote:
> > > Functions that are exported using EXPORT_SYMBOL, and thus are presumably 
> > > freely available for use in dynamically loaded modules, do not seem to 
> > > very often check the validity of their inputs.  For a simple example, 
> > > the following code from arch/arm/mach-realview/clock.c does not even check 
> > > that clk is not NULL:
> > > 
> > >  unsigned long clk_get_rate(struct clk *clk)
> > >  {
> > >         return clk->rate;
> > >  }
> > >  EXPORT_SYMBOL(clk_get_rate);
> > > 
> > > Is this a problem?
> > 
> > No, as long as all callers are not passing NULL :)
> > 
> > Seriously, it's not an issue, putting error checking for everything
> > causes a lot of extra code for no reason, as we can easily audit all
> > callers of these symbols, it is not always necessary to check the
> > paramters.
> 
> Who is we?

Us kernel developers.

> If the symbol is exported can't anyone write a kernel module 
> that uses the function?

Yes, and we can see their code as well when it is distributed.

> Is the policy that in that case they get what they deserve?

Yes, that would be a trivial thing to debug :)

thanks,

greg k-h