Re: [PATCH] usb: musb: sunxi: Explicitly release USB PHY on exit

[Jonathan Liu]

Hi,

On 10 October 2017 at 13:14, Bin Liu  wrote:
> On Tue, Oct 10, 2017 at 08:17:34AM +1100, Jonathan Liu wrote:
>> Hi,
>>
>> On 10 October 2017 at 01:23, Bin Liu  wrote:
>> > Hi,
>> >
>> > On Tue, Sep 26, 2017 at 09:39:23PM +1000, Jonathan Liu wrote:
>> >> This fixes a kernel oops when unloading the driver due to usb_put_phy
>> >> being called after usb_phy_generic_unregister when the device is
>> >> detached. Calling usb_phy_generic_unregister causes x->dev->driver to
>> >> be NULL in usb_put_phy and results in a NULL pointer dereference.
>> >>
>> >> As we are now explicitly managing the lifetime of usb_phy,
>> >> devm_usb_get_phy is changed to usb_get_phy and we call usb_put_phy in
>> >> the probe error path.
>> >>
>> >> Cc: sta...@vger.kernel.org # v4.3+
>> >> Signed-off-by: Jonathan Liu 
>> >> ---
>> >>  drivers/usb/musb/sunxi.c | 8 ++--
>> >>  1 file changed, 6 insertions(+), 2 deletions(-)
>> >>
>> >> diff --git a/drivers/usb/musb/sunxi.c b/drivers/usb/musb/sunxi.c
>> >> index c9a09b5bb6e5..8eed61042103 100644
>> >> --- a/drivers/usb/musb/sunxi.c
>> >> +++ b/drivers/usb/musb/sunxi.c
>> >> @@ -297,6 +297,8 @@ static int sunxi_musb_exit(struct musb *musb)
>> >>   if (test_bit(SUNXI_MUSB_FL_HAS_SRAM, >flags))
>> >>   sunxi_sram_release(musb->controller->parent);
>> >>
>> >> + usb_put_phy(glue->xceiv);
>> >
>> > Will devm_usb_put_phy() solve the issue too? Then you don't need the
>> > changes in sunxi_musb_probe() below.
>> >
>>
>> devm_usb_put_phy does solve the issue without changes in
>> sunxi_musb_probe but I think it is clearer that the lifetime is
>> explicitly managed if we don't mix implicit and explicit freeing of
>> resources.
>
> Then what is the purpose of the devm_* API?
>
> The original bug was that devm_usb_get_phy() is called in _probe, but
> devm_usb_put_phy() was never called, which caused the device ref count
> unbalanced. It is not related to implicit/explicit resource management.
>
> devm_* is recommended whenever applicable.
>

Ok. Will use devm_usb_put_phy in v2 patch.

> Regards,
> -Bin.
>

Regards,
Jonathan
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Re: [PATCH] usb: musb: sunxi: Explicitly release USB PHY on exit

[Bin Liu]

On Tue, Oct 10, 2017 at 08:17:34AM +1100, Jonathan Liu wrote:
> Hi,
> 
> On 10 October 2017 at 01:23, Bin Liu  wrote:
> > Hi,
> >
> > On Tue, Sep 26, 2017 at 09:39:23PM +1000, Jonathan Liu wrote:
> >> This fixes a kernel oops when unloading the driver due to usb_put_phy
> >> being called after usb_phy_generic_unregister when the device is
> >> detached. Calling usb_phy_generic_unregister causes x->dev->driver to
> >> be NULL in usb_put_phy and results in a NULL pointer dereference.
> >>
> >> As we are now explicitly managing the lifetime of usb_phy,
> >> devm_usb_get_phy is changed to usb_get_phy and we call usb_put_phy in
> >> the probe error path.
> >>
> >> Cc: sta...@vger.kernel.org # v4.3+
> >> Signed-off-by: Jonathan Liu 
> >> ---
> >>  drivers/usb/musb/sunxi.c | 8 ++--
> >>  1 file changed, 6 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/usb/musb/sunxi.c b/drivers/usb/musb/sunxi.c
> >> index c9a09b5bb6e5..8eed61042103 100644
> >> --- a/drivers/usb/musb/sunxi.c
> >> +++ b/drivers/usb/musb/sunxi.c
> >> @@ -297,6 +297,8 @@ static int sunxi_musb_exit(struct musb *musb)
> >>   if (test_bit(SUNXI_MUSB_FL_HAS_SRAM, >flags))
> >>   sunxi_sram_release(musb->controller->parent);
> >>
> >> + usb_put_phy(glue->xceiv);
> >
> > Will devm_usb_put_phy() solve the issue too? Then you don't need the
> > changes in sunxi_musb_probe() below.
> >
> 
> devm_usb_put_phy does solve the issue without changes in
> sunxi_musb_probe but I think it is clearer that the lifetime is
> explicitly managed if we don't mix implicit and explicit freeing of
> resources.

Then what is the purpose of the devm_* API?

The original bug was that devm_usb_get_phy() is called in _probe, but
devm_usb_put_phy() was never called, which caused the device ref count
unbalanced. It is not related to implicit/explicit resource management.

devm_* is recommended whenever applicable.

Regards,
-Bin.

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Re: [PATCH] usb: musb: sunxi: Explicitly release USB PHY on exit

[Jonathan Liu]

Hi,

On 10 October 2017 at 01:23, Bin Liu  wrote:
> Hi,
>
> On Tue, Sep 26, 2017 at 09:39:23PM +1000, Jonathan Liu wrote:
>> This fixes a kernel oops when unloading the driver due to usb_put_phy
>> being called after usb_phy_generic_unregister when the device is
>> detached. Calling usb_phy_generic_unregister causes x->dev->driver to
>> be NULL in usb_put_phy and results in a NULL pointer dereference.
>>
>> As we are now explicitly managing the lifetime of usb_phy,
>> devm_usb_get_phy is changed to usb_get_phy and we call usb_put_phy in
>> the probe error path.
>>
>> Cc: sta...@vger.kernel.org # v4.3+
>> Signed-off-by: Jonathan Liu 
>> ---
>>  drivers/usb/musb/sunxi.c | 8 ++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/musb/sunxi.c b/drivers/usb/musb/sunxi.c
>> index c9a09b5bb6e5..8eed61042103 100644
>> --- a/drivers/usb/musb/sunxi.c
>> +++ b/drivers/usb/musb/sunxi.c
>> @@ -297,6 +297,8 @@ static int sunxi_musb_exit(struct musb *musb)
>>   if (test_bit(SUNXI_MUSB_FL_HAS_SRAM, >flags))
>>   sunxi_sram_release(musb->controller->parent);
>>
>> + usb_put_phy(glue->xceiv);
>
> Will devm_usb_put_phy() solve the issue too? Then you don't need the
> changes in sunxi_musb_probe() below.
>

devm_usb_put_phy does solve the issue without changes in
sunxi_musb_probe but I think it is clearer that the lifetime is
explicitly managed if we don't mix implicit and explicit freeing of
resources.

>> +
>>   return 0;
>>  }
>>
>> @@ -781,7 +783,7 @@ static int sunxi_musb_probe(struct platform_device *pdev)
>>   return PTR_ERR(glue->usb_phy);
>>   }
>>
>> - glue->xceiv = devm_usb_get_phy(>dev, USB_PHY_TYPE_USB2);
>> + glue->xceiv = usb_get_phy(USB_PHY_TYPE_USB2);
>>   if (IS_ERR(glue->xceiv)) {
>>   ret = PTR_ERR(glue->xceiv);
>>   dev_err(>dev, "Error getting usb-phy %d\n", ret);
>> @@ -803,11 +805,13 @@ static int sunxi_musb_probe(struct platform_device 
>> *pdev)
>>   if (IS_ERR(glue->musb_pdev)) {
>>   ret = PTR_ERR(glue->musb_pdev);
>>   dev_err(>dev, "Error registering musb dev: %d\n", ret);
>> - goto err_unregister_usb_phy;
>> + goto err_put_usb_phy;
>>   }
>>
>>   return 0;
>>
>> +err_put_usb_phy:
>> + usb_put_phy(glue->xceiv);
>>  err_unregister_usb_phy:
>>   usb_phy_generic_unregister(glue->usb_phy);
>>   return ret;
>> --
>> 2.13.2
>
> Regards,
> -Bin.

Regards,
Jonathan
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Re: [PATCH] usb: musb: sunxi: Explicitly release USB PHY on exit

[Bin Liu]

Hi,

On Tue, Sep 26, 2017 at 09:39:23PM +1000, Jonathan Liu wrote:
> This fixes a kernel oops when unloading the driver due to usb_put_phy
> being called after usb_phy_generic_unregister when the device is
> detached. Calling usb_phy_generic_unregister causes x->dev->driver to
> be NULL in usb_put_phy and results in a NULL pointer dereference.
> 
> As we are now explicitly managing the lifetime of usb_phy,
> devm_usb_get_phy is changed to usb_get_phy and we call usb_put_phy in
> the probe error path.
> 
> Cc: sta...@vger.kernel.org # v4.3+
> Signed-off-by: Jonathan Liu 
> ---
>  drivers/usb/musb/sunxi.c | 8 ++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/musb/sunxi.c b/drivers/usb/musb/sunxi.c
> index c9a09b5bb6e5..8eed61042103 100644
> --- a/drivers/usb/musb/sunxi.c
> +++ b/drivers/usb/musb/sunxi.c
> @@ -297,6 +297,8 @@ static int sunxi_musb_exit(struct musb *musb)
>   if (test_bit(SUNXI_MUSB_FL_HAS_SRAM, >flags))
>   sunxi_sram_release(musb->controller->parent);
>  
> + usb_put_phy(glue->xceiv);

Will devm_usb_put_phy() solve the issue too? Then you don't need the
changes in sunxi_musb_probe() below.

> +
>   return 0;
>  }
>  
> @@ -781,7 +783,7 @@ static int sunxi_musb_probe(struct platform_device *pdev)
>   return PTR_ERR(glue->usb_phy);
>   }
>  
> - glue->xceiv = devm_usb_get_phy(>dev, USB_PHY_TYPE_USB2);
> + glue->xceiv = usb_get_phy(USB_PHY_TYPE_USB2);
>   if (IS_ERR(glue->xceiv)) {
>   ret = PTR_ERR(glue->xceiv);
>   dev_err(>dev, "Error getting usb-phy %d\n", ret);
> @@ -803,11 +805,13 @@ static int sunxi_musb_probe(struct platform_device 
> *pdev)
>   if (IS_ERR(glue->musb_pdev)) {
>   ret = PTR_ERR(glue->musb_pdev);
>   dev_err(>dev, "Error registering musb dev: %d\n", ret);
> - goto err_unregister_usb_phy;
> + goto err_put_usb_phy;
>   }
>  
>   return 0;
>  
> +err_put_usb_phy:
> + usb_put_phy(glue->xceiv);
>  err_unregister_usb_phy:
>   usb_phy_generic_unregister(glue->usb_phy);
>   return ret;
> -- 
> 2.13.2

Regards,
-Bin.
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Re: [PATCH] usb: musb: sunxi: Explicitly release USB PHY on exit

[Jonathan Liu]

Hi,

On 26 September 2017 at 21:39, Jonathan Liu  wrote:
> This fixes a kernel oops when unloading the driver due to usb_put_phy
> being called after usb_phy_generic_unregister when the device is
> detached. Calling usb_phy_generic_unregister causes x->dev->driver to
> be NULL in usb_put_phy and results in a NULL pointer dereference.
>
> As we are now explicitly managing the lifetime of usb_phy,
> devm_usb_get_phy is changed to usb_get_phy and we call usb_put_phy in
> the probe error path.
>
> Cc: sta...@vger.kernel.org # v4.3+
> Signed-off-by: Jonathan Liu 
> ---
>  drivers/usb/musb/sunxi.c | 8 ++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/musb/sunxi.c b/drivers/usb/musb/sunxi.c
> index c9a09b5bb6e5..8eed61042103 100644
> --- a/drivers/usb/musb/sunxi.c
> +++ b/drivers/usb/musb/sunxi.c
> @@ -297,6 +297,8 @@ static int sunxi_musb_exit(struct musb *musb)
> if (test_bit(SUNXI_MUSB_FL_HAS_SRAM, >flags))
> sunxi_sram_release(musb->controller->parent);
>
> +   usb_put_phy(glue->xceiv);
> +
> return 0;
>  }
>
> @@ -781,7 +783,7 @@ static int sunxi_musb_probe(struct platform_device *pdev)
> return PTR_ERR(glue->usb_phy);
> }
>
> -   glue->xceiv = devm_usb_get_phy(>dev, USB_PHY_TYPE_USB2);
> +   glue->xceiv = usb_get_phy(USB_PHY_TYPE_USB2);
> if (IS_ERR(glue->xceiv)) {
> ret = PTR_ERR(glue->xceiv);
> dev_err(>dev, "Error getting usb-phy %d\n", ret);
> @@ -803,11 +805,13 @@ static int sunxi_musb_probe(struct platform_device 
> *pdev)
> if (IS_ERR(glue->musb_pdev)) {
> ret = PTR_ERR(glue->musb_pdev);
> dev_err(>dev, "Error registering musb dev: %d\n", ret);
> -   goto err_unregister_usb_phy;
> +   goto err_put_usb_phy;
> }
>
> return 0;
>
> +err_put_usb_phy:
> +   usb_put_phy(glue->xceiv);
>  err_unregister_usb_phy:
> usb_phy_generic_unregister(glue->usb_phy);
> return ret;
> --
> 2.13.2
>

Another way I could fix this would be to check if x->dev->driver is
NULL before dereferencing in usb_put_phy but I am not sure if this
breaks any expectations in the USB subsystem...

Regards,
Jonathan
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[PATCH] usb: musb: sunxi: Explicitly release USB PHY on exit

[Jonathan Liu]

This fixes a kernel oops when unloading the driver due to usb_put_phy
being called after usb_phy_generic_unregister when the device is
detached. Calling usb_phy_generic_unregister causes x->dev->driver to
be NULL in usb_put_phy and results in a NULL pointer dereference.

As we are now explicitly managing the lifetime of usb_phy,
devm_usb_get_phy is changed to usb_get_phy and we call usb_put_phy in
the probe error path.

Cc: sta...@vger.kernel.org # v4.3+
Signed-off-by: Jonathan Liu 
---
 drivers/usb/musb/sunxi.c | 8 ++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/musb/sunxi.c b/drivers/usb/musb/sunxi.c
index c9a09b5bb6e5..8eed61042103 100644
--- a/drivers/usb/musb/sunxi.c
+++ b/drivers/usb/musb/sunxi.c
@@ -297,6 +297,8 @@ static int sunxi_musb_exit(struct musb *musb)
if (test_bit(SUNXI_MUSB_FL_HAS_SRAM, >flags))
sunxi_sram_release(musb->controller->parent);
 
+   usb_put_phy(glue->xceiv);
+
return 0;
 }
 
@@ -781,7 +783,7 @@ static int sunxi_musb_probe(struct platform_device *pdev)
return PTR_ERR(glue->usb_phy);
}
 
-   glue->xceiv = devm_usb_get_phy(>dev, USB_PHY_TYPE_USB2);
+   glue->xceiv = usb_get_phy(USB_PHY_TYPE_USB2);
if (IS_ERR(glue->xceiv)) {
ret = PTR_ERR(glue->xceiv);
dev_err(>dev, "Error getting usb-phy %d\n", ret);
@@ -803,11 +805,13 @@ static int sunxi_musb_probe(struct platform_device *pdev)
if (IS_ERR(glue->musb_pdev)) {
ret = PTR_ERR(glue->musb_pdev);
dev_err(>dev, "Error registering musb dev: %d\n", ret);
-   goto err_unregister_usb_phy;
+   goto err_put_usb_phy;
}
 
return 0;
 
+err_put_usb_phy:
+   usb_put_phy(glue->xceiv);
 err_unregister_usb_phy:
usb_phy_generic_unregister(glue->usb_phy);
return ret;
-- 
2.13.2

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