linux-kernel - Re: [PATCH 2/2] cxl/region: Fix missing put_device(region

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Date: Mon, 29 Apr 2024 13:17:03 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Li Zhijian <lizhijian@...itsu.com>
Cc: 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, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] cxl/region: Fix missing put_device(region_dev)

On Mon, Apr 29, 2024 at 09:31:54AM +0800, Li Zhijian wrote:
> >         mutex_lock(&cxlrd->range_lock);
> >         region_dev = device_find_child(&cxlrd->cxlsd.cxld.dev, hpa,
> >                                        match_region_by_range);
> >         if (!region_dev)
> >                 cxlr = construct_region(cxlrd, cxled);
> >         else
> >                 cxlr = to_cxl_region(region_dev);
> >         mutex_unlock(&cxlrd->range_lock);
> >
> >         rc = PTR_ERR_OR_ZERO(cxlr);
> >         if (rc)
> >                 goto out;
> >
> >         if (!region_dev)
> >                 region_dev = &cxlr->dev;
> 
> When to_cxl_region(region_dev) fails,
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
to_cxl_region() will return NULL if "region_dev" is not a region device.

  2215  static struct cxl_region *to_cxl_region(struct device *dev)
  2216  {
  2217          if (dev_WARN_ONCE(dev, dev->type != &cxl_region_type,
  2218                            "not a cxl_region device\n"))
  2219                  return NULL;
  2220  
  2221          return container_of(dev, struct cxl_region, dev);
  2222  }

It won't fail.

If it does fail, we're already in bad shape and it's not worth worrying
about resource leaks at that point.

regards,
dan carpenter