linux-kernel - Re: [PATCH] print_worker_info: Handle pointer with more care

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Message-ID: <20130816161229.GI2505@htj.dyndns.org>
Date:	Fri, 16 Aug 2013 12:12:29 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Richard Weinberger <richard@....at>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] print_worker_info: Handle pointer with more care

On Fri, Aug 16, 2013 at 05:56:46PM +0200, Richard Weinberger wrote:
> The function has a nice comment:
> /*
>  * This function is called without any synchronization and @task
>  * could be in any state.  Be careful with dereferences.
>  */
> 
> But a few lines later it blindly dereferences a few pointers.
> E.g. It can happen that the worker function is already done,
> then worker->current_pwq is NULL.
...
>  	probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
>  	probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
> +	if (!pwq)
> +		goto print;
> +
>  	probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
> +	if (!wq)
> +		goto print;
> +

But none of the above are dereferences.  &ptr->field is offset
calculation, not a dereference.

Thanks.

-- 
tejun
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