linux-kernel - Re: /proc/kallsyms race vs module unload

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Message-ID: <20070313230753.GB5623@martell.zuzino.mipt.ru>
Date:	Wed, 14 Mar 2007 02:07:53 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Paulo Marques <pmarques@...popie.com>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org
Subject: Re: /proc/kallsyms race vs module unload

On Tue, Mar 13, 2007 at 06:49:50PM +0000, Paulo Marques wrote:
> Alexey Dobriyan wrote:
> >[...]
> >What happens is that module_get_kallsym() drops module_mutex,
> >returns "struct module *", module unloaded, "struct module *"
> >used.
>
> The only use for the "struct module *" is to display the name of the
> module.

Ehh?

> This can be solved by adding a "char mod_name[MODULE_NAME_LEN];" field
> to "kallsym_iter" and copy the name of the module over, while still
> holding module_mutex. It would be slightly slower, but safer.

	iter->owner = module_get_kallsym(iter->pos - kallsyms_num_syms,
					 &iter->value, &iter->type,
					 iter->name, sizeof(iter->name));
	if (iter->owner == NULL)
		return 0;

	/* Label it "global" if it is exported, "local" if not exported. */
	iter->type = is_exported(iter->name, iter->owner)
					     ^^^^^^^^^^^

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