2017-09-26 11:37:47

by Jonathan Liu

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

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: [email protected] # v4.3+
Signed-off-by: Jonathan Liu <[email protected]>
---
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, &glue->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(&pdev->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(&pdev->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(&pdev->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

2017-09-26 11:42:13

by Jonathan Liu

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

Hi,

On 26 September 2017 at 21:39, Jonathan Liu <[email protected]> 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: [email protected] # v4.3+
> Signed-off-by: Jonathan Liu <[email protected]>
> ---
> 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, &glue->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(&pdev->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(&pdev->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(&pdev->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