Re: [PATCH 2/2] cxl/region: Fix missing put_device(region_dev)

["Zhijian Li (Fujitsu)" <lizhijian@fujitsu.com>]

On 29/04/2024 09:31, 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);


Think again, PTR_ERR_OR_ZERO() here should be IS_ERR_OR_NULL()?
PTR_ERR_OR_ZERO() returns 0 if cxlr is NULL, but the cxlr will be dereferenced later.



>>          if (rc)
>>                  goto out;
>>
>>          if (!region_dev)
>>                  region_dev = &cxlr->dev;
> 
> When to_cxl_region(region_dev) fails, put_device(region_dev) should be
> called to decrease the reference count added by device_find_child().
> 
> Simply put_device(region_dev) if region_dev is valid in the error path.
> 
> Fixes: a32320b71f08 ("cxl/region: Add region autodiscovery")
> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> ---
>   drivers/cxl/core/region.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 3c80aa263a65..75390865382f 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3117,8 +3117,9 @@ int cxl_add_to_region(struct cxl_port *root, struct cxl_endpoint_decoder *cxled)
>   				p->res);
>   	}
>   
> -	put_device(region_dev);
>   out:
> +	if (region_dev)
> +		put_device(region_dev);
>   	put_device(cxlrd_dev);
>   	return rc;
>   }