linux-kernel - Re: [PATCH 1/2] cxl/region: Fix potential invalid pointer dereference

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Date: Mon, 29 Apr 2024 09:50:36 +0200
From: Markus Elfring <Markus.Elfring@....de>
To: Li Zhijian <lizhijian@...itsu.com>, linux-cxl@...r.kernel.org,
 kernel-janitors@...r.kernel.org,
 Alison Schofield <alison.schofield@...el.com>,
 Dan Williams <dan.j.williams@...el.com>, Dave Jiang <dave.jiang@...el.com>,
 Davidlohr Bueso <dave@...olabs.net>, Ira Weiny <ira.weiny@...el.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Vishal Verma <vishal.l.verma@...el.com>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] cxl/region: Fix potential invalid pointer dereference

I would usually expect a corresponding cover letter for patch series.


> construct_region() could return a PTR_ERR() which cannot be derefernced.

I hope that a typo will be avoided in the last word of this sentence.


> Moving the dereference behind the error checking to make sure the
> pointer is valid.

Please choose an imperative wording for an improved change description.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.9-rc5#n94


…
> +++ b/drivers/cxl/core/region.c
> @@ -3086,10 +3086,9 @@ int cxl_add_to_region(struct cxl_port *root, struct cxl_endpoint_decoder *cxled)
>  	mutex_lock(&cxlrd->range_lock);
>  	region_dev = device_find_child(&cxlrd->cxlsd.cxld.dev, hpa,
>  				       match_region_by_range);
> -	if (!region_dev) {
> +	if (!region_dev)
>  		cxlr = construct_region(cxlrd, cxled);
> -		region_dev = &cxlr->dev;
> -	} else
> +	else
>  		cxlr = to_cxl_region(region_dev);
>  	mutex_unlock(&cxlrd->range_lock);

I suggest to simplify such source code by using a conditional operator expression.

Regards,
Markus