[PATCH v2] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

[PATCH v2] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

[Zeng Heng]

There is warning report about of_node refcount leak
while probing mdio device:

OF: ERROR: memory leak, expected refcount 1 instead of 2,
of_node_get()/of_node_put() unbalanced - destroy cset entry:
attach overlay node /spi/soc@0/mdio@710700c0/ethernet@4

In of_mdiobus_register_device(), we increase fwnode refcount
by fwnode_handle_get() before associating the of_node with
mdio device, but it has never been decreased in normal path.
Since that, in mdio_device_release(), it needs to call
fwnode_handle_put() in addition instead of calling kfree()
directly.

After above, just calling mdio_device_free() in the error handle
path of of_mdiobus_register_device() is enough to keep the
refcount balanced.

Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
---
 changes in v2:
  - Add operation about setting device node as NULL-pointer.
    There is no practical changes.
  - Add reviewed-by tag.
---
 drivers/net/mdio/of_mdio.c    | 3 ++-
 drivers/net/phy/mdio_device.c | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
index 796e9c7857d0..510822d6d0d9 100644
--- a/drivers/net/mdio/of_mdio.c
+++ b/drivers/net/mdio/of_mdio.c
@@ -68,8 +68,9 @@ static int of_mdiobus_register_device(struct mii_bus *mdio,
 	/* All data is now stored in the mdiodev struct; register it. */
 	rc = mdio_device_register(mdiodev);
 	if (rc) {
+		device_set_node(&mdiodev->dev, NULL);
+		fwnode_handle_put(fwnode);
 		mdio_device_free(mdiodev);
-		of_node_put(child);
 		return rc;
 	}
 
diff --git a/drivers/net/phy/mdio_device.c b/drivers/net/phy/mdio_device.c
index 250742ffdfd9..044828d081d2 100644
--- a/drivers/net/phy/mdio_device.c
+++ b/drivers/net/phy/mdio_device.c
@@ -21,6 +21,7 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/unistd.h>
+#include <linux/property.h>
 
 void mdio_device_free(struct mdio_device *mdiodev)
 {
@@ -30,6 +31,7 @@ EXPORT_SYMBOL(mdio_device_free);
 
 static void mdio_device_release(struct device *dev)
 {
+	fwnode_handle_put(dev->fwnode);
 	kfree(to_mdio_device(dev));
 }
 
-- 
2.25.1

Re: [PATCH v2] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

[Paolo Abeni]

Hello,
On Sat, 2022-12-03 at 15:34 +0800, Zeng Heng wrote:
> There is warning report about of_node refcount leak
> while probing mdio device:
> 
> OF: ERROR: memory leak, expected refcount 1 instead of 2,
> of_node_get()/of_node_put() unbalanced - destroy cset entry:
> attach overlay node /spi/soc@0/mdio@710700c0/ethernet@4
> 
> In of_mdiobus_register_device(), we increase fwnode refcount
> by fwnode_handle_get() before associating the of_node with
> mdio device, but it has never been decreased in normal path.
> Since that, in mdio_device_release(), it needs to call
> fwnode_handle_put() in addition instead of calling kfree()
> directly.
> 
> After above, just calling mdio_device_free() in the error handle
> path of of_mdiobus_register_device() is enough to keep the
> refcount balanced.
> 
> Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
>  changes in v2:
>   - Add operation about setting device node as NULL-pointer.
>     There is no practical changes.
>   - Add reviewed-by tag.
> ---
>  drivers/net/mdio/of_mdio.c    | 3 ++-
>  drivers/net/phy/mdio_device.c | 2 ++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
> index 796e9c7857d0..510822d6d0d9 100644
> --- a/drivers/net/mdio/of_mdio.c
> +++ b/drivers/net/mdio/of_mdio.c
> @@ -68,8 +68,9 @@ static int of_mdiobus_register_device(struct mii_bus *mdio,
>  	/* All data is now stored in the mdiodev struct; register it. */
>  	rc = mdio_device_register(mdiodev);
>  	if (rc) {
> +		device_set_node(&mdiodev->dev, NULL);
> +		fwnode_handle_put(fwnode);
>  		mdio_device_free(mdiodev);
> -		of_node_put(child);
>  		return rc;
>  	}
>  
> diff --git a/drivers/net/phy/mdio_device.c b/drivers/net/phy/mdio_device.c
> index 250742ffdfd9..044828d081d2 100644
> --- a/drivers/net/phy/mdio_device.c
> +++ b/drivers/net/phy/mdio_device.c
> @@ -21,6 +21,7 @@
>  #include <linux/slab.h>
>  #include <linux/string.h>
>  #include <linux/unistd.h>
> +#include <linux/property.h>
>  
>  void mdio_device_free(struct mdio_device *mdiodev)
>  {
> @@ -30,6 +31,7 @@ EXPORT_SYMBOL(mdio_device_free);
>  
>  static void mdio_device_release(struct device *dev)
>  {
> +	fwnode_handle_put(dev->fwnode);
>  	kfree(to_mdio_device(dev));
>  }
> 
The patch LGTM, but I'll wait a bit more just in case Andrew want to
comment on it.

Cheers,

Paolo

Re: [PATCH v2] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

[Russell King (Oracle)]

On Sat, Dec 03, 2022 at 03:34:41PM +0800, Zeng Heng wrote:
> There is warning report about of_node refcount leak
> while probing mdio device:
> 
> OF: ERROR: memory leak, expected refcount 1 instead of 2,
> of_node_get()/of_node_put() unbalanced - destroy cset entry:
> attach overlay node /spi/soc@0/mdio@710700c0/ethernet@4
> 
> In of_mdiobus_register_device(), we increase fwnode refcount
> by fwnode_handle_get() before associating the of_node with
> mdio device, but it has never been decreased in normal path.
> Since that, in mdio_device_release(), it needs to call
> fwnode_handle_put() in addition instead of calling kfree()
> directly.
> 
> After above, just calling mdio_device_free() in the error handle
> path of of_mdiobus_register_device() is enough to keep the
> refcount balanced.
> 
> Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>

LGTM, thanks!

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

Re: [PATCH v2] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

[Zeng Heng]

On 2022/12/6 19:34, Paolo Abeni wrote:
> Hello,
> On Sat, 2022-12-03 at 15:34 +0800, Zeng Heng wrote:
>> There is warning report about of_node refcount leak
>> while probing mdio device:
>>
>> OF: ERROR: memory leak, expected refcount 1 instead of 2,
>> of_node_get()/of_node_put() unbalanced - destroy cset entry:
>> attach overlay node /spi/soc@0/mdio@710700c0/ethernet@4
>>
>> In of_mdiobus_register_device(), we increase fwnode refcount
>> by fwnode_handle_get() before associating the of_node with
>> mdio device, but it has never been decreased in normal path.
>> Since that, in mdio_device_release(), it needs to call
>> fwnode_handle_put() in addition instead of calling kfree()
>> directly.
>>
>> After above, just calling mdio_device_free() in the error handle
>> path of of_mdiobus_register_device() is enough to keep the
>> refcount balanced.
>>
>> Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
>> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
>> Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
>> ---
>>   changes in v2:
>>    - Add operation about setting device node as NULL-pointer.
>>      There is no practical changes.
>>    - Add reviewed-by tag.
>> ---
>>   drivers/net/mdio/of_mdio.c    | 3 ++-
>>   drivers/net/phy/mdio_device.c | 2 ++
>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
>> index 796e9c7857d0..510822d6d0d9 100644
>> --- a/drivers/net/mdio/of_mdio.c
>> +++ b/drivers/net/mdio/of_mdio.c
>> @@ -68,8 +68,9 @@ static int of_mdiobus_register_device(struct mii_bus *mdio,
>>   	/* All data is now stored in the mdiodev struct; register it. */
>>   	rc = mdio_device_register(mdiodev);
>>   	if (rc) {
>> +		device_set_node(&mdiodev->dev, NULL);
>> +		fwnode_handle_put(fwnode);
>>   		mdio_device_free(mdiodev);
>> -		of_node_put(child);
>>   		return rc;
>>   	}
>>   
>> diff --git a/drivers/net/phy/mdio_device.c b/drivers/net/phy/mdio_device.c
>> index 250742ffdfd9..044828d081d2 100644
>> --- a/drivers/net/phy/mdio_device.c
>> +++ b/drivers/net/phy/mdio_device.c
>> @@ -21,6 +21,7 @@
>>   #include <linux/slab.h>
>>   #include <linux/string.h>
>>   #include <linux/unistd.h>
>> +#include <linux/property.h>
>>   
>>   void mdio_device_free(struct mdio_device *mdiodev)
>>   {
>> @@ -30,6 +31,7 @@ EXPORT_SYMBOL(mdio_device_free);
>>   
>>   static void mdio_device_release(struct device *dev)
>>   {
>> +	fwnode_handle_put(dev->fwnode);
>>   	kfree(to_mdio_device(dev));
>>   }
>>
> The patch LGTM, but I'll wait a bit more just in case Andrew want to
> comment on it.
>
> Cheers,
>
> Paolo
+CC Yang Yingliang <yangyingliang@huawei.com>

Re: [PATCH v2] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by Paolo Abeni <pabeni@redhat.com>:

On Sat, 3 Dec 2022 15:34:41 +0800 you wrote:
> There is warning report about of_node refcount leak
> while probing mdio device:
> 
> OF: ERROR: memory leak, expected refcount 1 instead of 2,
> of_node_get()/of_node_put() unbalanced - destroy cset entry:
> attach overlay node /spi/soc@0/mdio@710700c0/ethernet@4
> 
> [...]

Here is the summary with links:
  - [v2] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()
    https://git.kernel.org/netdev/net/c/cb37617687f2

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
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Re: [PATCH v2] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

[luoxuanqiang]

Hi Heng,

在 2022/12/3 15:34, Zeng Heng 写道:
> There is warning report about of_node refcount leak
> while probing mdio device:
>
> OF: ERROR: memory leak, expected refcount 1 instead of 2,
> of_node_get()/of_node_put() unbalanced - destroy cset entry:
> attach overlay node /spi/soc@0/mdio@710700c0/ethernet@4
>
> In of_mdiobus_register_device(), we increase fwnode refcount
> by fwnode_handle_get() before associating the of_node with
> mdio device, but it has never been decreased in normal path.
> Since that, in mdio_device_release(), it needs to call
> fwnode_handle_put() in addition instead of calling kfree()
> directly.
>
> After above, just calling mdio_device_free() in the error handle
> path of of_mdiobus_register_device() is enough to keep the
> refcount balanced.
>
> Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
>   changes in v2:
>    - Add operation about setting device node as NULL-pointer.
>      There is no practical changes.
>    - Add reviewed-by tag.
> ---
>   drivers/net/mdio/of_mdio.c    | 3 ++-
>   drivers/net/phy/mdio_device.c | 2 ++
>   2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
> index 796e9c7857d0..510822d6d0d9 100644
> --- a/drivers/net/mdio/of_mdio.c
> +++ b/drivers/net/mdio/of_mdio.c
> @@ -68,8 +68,9 @@ static int of_mdiobus_register_device(struct mii_bus *mdio,
>   	/* All data is now stored in the mdiodev struct; register it. */
>   	rc = mdio_device_register(mdiodev);
>   	if (rc) {
> +		device_set_node(&mdiodev->dev, NULL);
> +		fwnode_handle_put(fwnode);
According to my understanding, the process flow of mdio_device_free() is
as follows:
mdio_device_free()
     -> put_device()
         ->kobject_put()
             ->kobject_release()
                 ->device_release()
                     ->mdio_device_release()
                     //Here, it will be called once fwnode_handle_put();

Why is it necessary to add fwnode_handle_put(fwnode) again here? In the
body of your email, you described that mdio_device_free() is sufficient
to keep refcount balanced, and it was not added in the v1.
Could you please explain the reason for this?
I am looking forward to your response :)

Thanks
Xuanqiang
>   		mdio_device_free(mdiodev);
> -		of_node_put(child);
>   		return rc;
>   	}
>   
> diff --git a/drivers/net/phy/mdio_device.c b/drivers/net/phy/mdio_device.c
> index 250742ffdfd9..044828d081d2 100644
> --- a/drivers/net/phy/mdio_device.c
> +++ b/drivers/net/phy/mdio_device.c
> @@ -21,6 +21,7 @@
>   #include <linux/slab.h>
>   #include <linux/string.h>
>   #include <linux/unistd.h>
> +#include <linux/property.h>
>   
>   void mdio_device_free(struct mdio_device *mdiodev)
>   {
> @@ -30,6 +31,7 @@ EXPORT_SYMBOL(mdio_device_free);
>   
>   static void mdio_device_release(struct device *dev)
>   {
> +	fwnode_handle_put(dev->fwnode);
>   	kfree(to_mdio_device(dev));
>   }
>   

Re: [PATCH v2] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

[luoxuanqiang]

Hi Heng,

在 2024/11/22 15:59, luoxuanqiang 写道:
> Hi Heng,
>
> 在 2022/12/3 15:34, Zeng Heng 写道:
>> There is warning report about of_node refcount leak
>> while probing mdio device:
>>
>> OF: ERROR: memory leak, expected refcount 1 instead of 2,
>> of_node_get()/of_node_put() unbalanced - destroy cset entry:
>> attach overlay node /spi/soc@0/mdio@710700c0/ethernet@4
>>
>> In of_mdiobus_register_device(), we increase fwnode refcount
>> by fwnode_handle_get() before associating the of_node with
>> mdio device, but it has never been decreased in normal path.
>> Since that, in mdio_device_release(), it needs to call
>> fwnode_handle_put() in addition instead of calling kfree()
>> directly.
>>
>> After above, just calling mdio_device_free() in the error handle
>> path of of_mdiobus_register_device() is enough to keep the
>> refcount balanced.
>>
>> Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
>> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
>> Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
>> ---
>>   changes in v2:
>>    - Add operation about setting device node as NULL-pointer.
>>      There is no practical changes.
>>    - Add reviewed-by tag.
>> ---
>>   drivers/net/mdio/of_mdio.c    | 3 ++-
>>   drivers/net/phy/mdio_device.c | 2 ++
>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
>> index 796e9c7857d0..510822d6d0d9 100644
>> --- a/drivers/net/mdio/of_mdio.c
>> +++ b/drivers/net/mdio/of_mdio.c
>> @@ -68,8 +68,9 @@ static int of_mdiobus_register_device(struct 
>> mii_bus *mdio,
>>       /* All data is now stored in the mdiodev struct; register it. */
>>       rc = mdio_device_register(mdiodev);
>>       if (rc) {
>> +        device_set_node(&mdiodev->dev, NULL);
>> +        fwnode_handle_put(fwnode);
> According to my understanding, the process flow of mdio_device_free() is
> as follows:
> mdio_device_free()
>     -> put_device()
>         ->kobject_put()
>             ->kobject_release()
>                 ->device_release()
>                     ->mdio_device_release()
>                     //Here, it will be called once fwnode_handle_put();
>
> Why is it necessary to add fwnode_handle_put(fwnode) again here? In the
> body of your email, you described that mdio_device_free() is sufficient
> to keep refcount balanced, and it was not added in the v1.
> Could you please explain the reason for this?
> I am looking forward to your response :)
>
> Thanks
> Xuanqiang
I noticed that I had missed the fact that you had already disconnected
the relationship between dev and node by calling
device_set_node(&mdiodev->dev, NULL). Even though it would go through
fwnode_handle_put() again, it would not have any effect.

Thanks
>>           mdio_device_free(mdiodev);
>> -        of_node_put(child);
>>           return rc;
>>       }
>>   diff --git a/drivers/net/phy/mdio_device.c 
>> b/drivers/net/phy/mdio_device.c
>> index 250742ffdfd9..044828d081d2 100644
>> --- a/drivers/net/phy/mdio_device.c
>> +++ b/drivers/net/phy/mdio_device.c
>> @@ -21,6 +21,7 @@
>>   #include <linux/slab.h>
>>   #include <linux/string.h>
>>   #include <linux/unistd.h>
>> +#include <linux/property.h>
>>     void mdio_device_free(struct mdio_device *mdiodev)
>>   {
>> @@ -30,6 +31,7 @@ EXPORT_SYMBOL(mdio_device_free);
>>     static void mdio_device_release(struct device *dev)
>>   {
>> +    fwnode_handle_put(dev->fwnode);
>>       kfree(to_mdio_device(dev));
>>   }
>