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SubjectRe: [PATCH 2/2] cxl/region: Fix missing put_device(region_dev)
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TBH, even though this patch seems correct, there are still a few
to_cxl_region() callers where they dereference the return value directly
without checking if it's NULL.

So I'm fine to drop this one because to_cxl_region() will trigger a WARN before
returning NULL.

static struct cxl_region *to_cxl_region(struct device *dev)
{
if (dev_WARN_ONCE(dev, dev->type != &cxl_region_type,
"not a cxl_region device\n"))
return NULL;

return container_of(dev, struct cxl_region, dev);
}


Let me know your thoughts.

Thanks
Zhijian

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);
>> 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;
> }
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