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

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Date: Mon, 29 Apr 2024 09:05:55 -0700
From: Ira Weiny <ira.weiny@...el.com>
To: Li Zhijian <lizhijian@...itsu.com>, <dave@...olabs.net>,
	<jonathan.cameron@...wei.com>, <dave.jiang@...el.com>,
	<alison.schofield@...el.com>, <vishal.l.verma@...el.com>,
	<ira.weiny@...el.com>, <dan.j.williams@...el.com>,
	<linux-cxl@...r.kernel.org>
CC: <linux-kernel@...r.kernel.org>, Li Zhijian <lizhijian@...itsu.com>
Subject: Re: [PATCH 1/2] cxl/region: Fix potential invalid pointer dereference

Li Zhijian wrote:
> construct_region() could return a PTR_ERR() which cannot be derefernced.
                                                             ^^^^
                                                             dereferenced

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

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

> Fixes: a32320b71f08 ("cxl/region: Add region autodiscovery")
> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>
> ---
>  drivers/cxl/core/region.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 8535718a20f0..3c80aa263a65 100644
> --- a/drivers/cxl/core/region.c
> +++ 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);
>  
> @@ -3097,6 +3096,9 @@ int cxl_add_to_region(struct cxl_port *root, struct cxl_endpoint_decoder *cxled)
>  	if (rc)
>  		goto out;
>  
> +	if (!region_dev)
> +		region_dev = &cxlr->dev;
> +
>  	attach_target(cxlr, cxled, -1, TASK_UNINTERRUPTIBLE);
>  
>  	down_read(&cxl_region_rwsem);
> -- 
> 2.29.2
>