linux-kernel - Re: PATCH [1/1]: Don't return symbol lables in init sections after they have been freed

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Message-ID: <20080306051337.GH16166@kroah.com>
Date:	Wed, 5 Mar 2008 21:13:37 -0800
From:	Greg KH <greg@...ah.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Robin Getz <rgetz@...ckfin.uclinux.org>, rusty@...tcorp.com.au,
	linux-kernel@...r.kernel.org, Dave Hansen <haveblue@...ibm.com>
Subject: Re: PATCH [1/1]: Don't return symbol lables in init sections after
	they have been freed

On Tue, Mar 04, 2008 at 04:05:01PM -0800, Andrew Morton wrote:
> On Tue, 4 Mar 2008 18:47:15 -0500
> Robin Getz <rgetz@...ckfin.uclinux.org> wrote:
> 
> > From: Robin Getz <rgetz@...ckfin.uclinux.org>
> > 
> > Today, when module names are looked up, we do not qualify them (check to see 
> > if the init section is still active or not). This can lead to problems when 
> > kernel modules get loaded into the same address that the kernel init section 
> > (or other module's init section was at). We sometimes return the old / no 
> > lomnger there 
> > 
> > This leads to bogus OOPS messages, and developers wasting their time looking 
> > for problems (in the kernel init section) where there are none (since it was 
> > a module).
> > 
> > This patch qualifies the addresses, to make sure the addresses are still valid 
> > before label/offset.
> > 
> > Signed-off-by: Robin Getz <rgetz@...ckfin.uclinux.org>
> > 
> > ---
> > 
> >  linux-2.6.x/kernel/kallsyms.c |    3 ++-
> >  linux-2.6.x/kernel/module.c   |    3 ++-
> >  2 files changed, 4 insertions(+), 2 deletions(-)
> > 
> > Index: linux-2.6.x/kernel/kallsyms.c
> > ===================================================================
> > --- linux-2.6.x/kernel/kallsyms.c	(revision 4212)
> > +++ linux-2.6.x/kernel/kallsyms.c	(working copy)
> > @@ -42,7 +42,8 @@
> >  
> >  static inline int is_kernel_inittext(unsigned long addr)
> >  {
> > -	if (addr >= (unsigned long)_sinittext
> > +	if (system_state == SYSTEM_BOOTING
> > +	    && addr >= (unsigned long)_sinittext
> >  	    && addr <= (unsigned long)_einittext)
> >  		return 1;
> >  	return 0;
> > Index: linux-2.6.x/kernel/module.c
> > ===================================================================
> > --- linux-2.6.x/kernel/module.c	(revision 4212)
> > +++ linux-2.6.x/kernel/module.c	(working copy)
> > @@ -2121,7 +2121,8 @@
> >  	struct module *mod;
> >  
> >  	list_for_each_entry(mod, &modules, list) {
> > -		if (within(addr, mod->module_init, mod->init_size)
> > +		if ((within(addr, mod->module_init, mod->init_size)
> > +		     && mod->state == MODULE_STATE_COMING)
> >  		    || within(addr, mod->module_core, mod->core_size)) {
> >  			if (modname)
> >  				*modname = mod->name;
> 
> Both of the above additions could do with a comment explaining what's going
> on.
> 
> The first one perhaps should use the more specific initmem_now_dynamic
> which is added by
> gregkh-driver-warn-when-statically-allocated-kobjects-are-used.patch from
> Greg's driver tree.  If the intent is to merge that - if not perhaps it can
> be split up.

The intent wasn't to merge that, as it seemed like a big hack.  But if
people don't mind, I have no objection to it going in.

thanks,

greg k-h
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