linux-kernel - Re: [PATCH] staging: greybus: codecs: fix type confusion with dedicated list iterator variable

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Date:   Mon, 21 Mar 2022 10:06:13 +0100
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Vaibhav Agarwal <vaibhav.sr@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        greybus-dev@...ts.linaro.org, linux-staging@...ts.linux.dev,
        Mark Greer <mgreer@...malcreek.com>,
        Johan Hovold <johan@...nel.org>, Alex Elder <elder@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mike Rapport <rppt@...nel.org>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: Re: [PATCH] staging: greybus: codecs: fix type confusion with
 dedicated list iterator variable


> On 21. Mar 2022, at 09:48, Dan Carpenter <dan.carpenter@...cle.com> wrote:
> 
> The subject says that it fixes a bug but it does not.

Thank you for your review!

I don't agree that this doesn't fix a bug:

> +		}
> 	}
> 	if (!data) {
> -		dev_err(dai->dev, "%s:%s DATA connection missing\n",
> -			dai->name, module->name);

Using 'module' when data == NULL is *guaranteed* to be a type confused
bogus pointer. It fundamentally can never be correct.

If I should still change the wording please let me know.

> +		dev_err(dai->dev, "%s DATA connection missing\n",
> +			dai->name);
> 		mutex_unlock(&codec->lock);
> 		return -ENODEV;
> 	}


> 
> On Sat, Mar 19, 2022 at 09:20:58PM +0100, Jakob Koschel wrote:
>> If the list does not exit early then data == NULL and 'module' does not
>> point to a valid list element.
>> Using 'module' in such a case is not valid and was therefore removed.
> 
> This paragraph is confusing jumble words.  Just say: "This code is fine".
> 
>> 
>> In preparation to limit the scope of the list iterator to the list
>> traversal loop, use a dedicated pointer pointing to the found element [1].
> 
> This paragraph is the information we need.  Just add something like
> "This patch has no effect on runtime".

As mentioned above, this code effects runtime (in one out of the two cases).

> 
> regards,
> dan carpenter

Thanks,
Jakob