linux-kernel - Re: [BUG 2.6.36-rc6] list corruption in module_bug

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Message-Id: <201010051544.52269.rusty@rustcorp.com.au>
Date:	Tue, 5 Oct 2010 15:44:51 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Arnd Bergmann <arnd@...db.de>, LKML <linux-kernel@...r.kernel.org>,
	Kay Sievers <kay.sievers@...y.org>,
	Brandon Philips <brandon@...p.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [BUG 2.6.36-rc6] list corruption in module_bug_finalize

On Tue, 5 Oct 2010 09:13:38 am Thomas Gleixner wrote:
> The patch below cures it.

Using module_mutex here is just lazy...  Here's 5c, go buy your own lock :)

>  	/*
> -	 * Strictly speaking this should have a spinlock to protect against
> -	 * traversals, but since we only traverse on BUG()s, a spinlock
> -	 * could potentially lead to deadlock and thus be counter-productive.
> +	 * We need to take module_mutex here to protect the list add, though
> +	 * it won't protect against a concurrent BUG().
>  	 */
> +	mutex_lock(&module_mutex);
>  	list_add(&mod->bug_list, &module_bug_list);
> +	mutex_unlock(&module_mutex);
>  
>  	return 0;
>  }
>  
>  void module_bug_cleanup(struct module *mod)
>  {
> +	mutex_lock(&module_mutex);
>  	list_del(&mod->bug_list);
> +	mutex_unlock(&module_mutex);
>  }
>  
>  #else
> 
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