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: <20080304160501.17d992f0.akpm@linux-foundation.org>
Date:	Tue, 4 Mar 2008 16:05:01 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Robin Getz <rgetz@...ckfin.uclinux.org>
Cc:	rusty@...tcorp.com.au, linux-kernel@...r.kernel.org,
	Greg KH <greg@...ah.com>, 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, 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.
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