linux-kernel - Re: [patch 00/16] timers: Plug debugobject leaks and use del_timer

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Date:	Mon, 24 Mar 2014 10:03:57 +0100
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch 00/16] timers: Plug debugobject leaks and use  del_timer_sync() in exit/teardown

On 2014-03-24 08:29, Julia Lawall wrote:
>> Another thing I saw is
>>
>> 	del_timer(&bla->timer);
>> 	....
>> 	kfree(&bla);
>
> In one case I saw the following:
>
>         if (isac->dch.timer.function != NULL) {
>                 del_timer(&isac->dch.timer);
>                 isac->dch.timer.function = NULL;
>         }
>         kfree(isac->mon_rx);
>         isac->mon_rx = NULL;
>
> Is the assignment isac->dch.timer.function = NULL good enough to 
> solve
> the problem?

No. It might lead to a NULL dereference when the other core wants
to call the callback. Same situation as in the other picture.

Thanks,

        tglx

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