Re: [PATCH] phy: tegra: xusb: Fix use-after-free issue

[Thierry Reding]

On Thu, May 04, 2023 at 01:54:46PM +0800, Haotien Hsu wrote:
> From: EJ Hsu <ejh@xxxxxxxxxx>
> 
> For the dual-role port, it will assign the phy dev to usb-phy dev and
> use the port dev driver as the dev driver of usb-phy.
> 
> When we try to destroy the port dev, it will destroy its dev driver
> as well. But we did not remove the reference from usb-phy dev. This
> might cause the use-after-free issue in KASAN.
> 
> Fixes: e8f7d2f409a1 ("phy: tegra: xusb: Add usb-phy support")
> Cc: stable@xxxxxxxxxxxxxxx
> 
> Signed-off-by: EJ Hsu <ejh@xxxxxxxxxx>
> Signed-off-by: Haotien Hsu <haotienh@xxxxxxxxxx>
> ---
>  drivers/phy/tegra/xusb.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/phy/tegra/xusb.c b/drivers/phy/tegra/xusb.c
> index 78045bd6c214..515298a9a433 100644
> --- a/drivers/phy/tegra/xusb.c
> +++ b/drivers/phy/tegra/xusb.c
> @@ -563,13 +563,6 @@ static int tegra_xusb_port_init(struct tegra_xusb_port *port,
>  
>  static void tegra_xusb_port_unregister(struct tegra_xusb_port *port)
>  {
> -	if (!IS_ERR_OR_NULL(port->usb_role_sw)) {
> -		of_platform_depopulate(&port->dev);
> -		usb_role_switch_unregister(port->usb_role_sw);
> -		cancel_work_sync(&port->usb_phy_work);
> -		usb_remove_phy(&port->usb_phy);
> -	}
> -
>  	if (port->ops->remove)
>  		port->ops->remove(port);
>  
> @@ -832,6 +825,14 @@ void tegra_xusb_usb2_port_remove(struct tegra_xusb_port *port)
>  {
>  	struct tegra_xusb_usb2_port *usb2 = to_usb2_port(port);
>  
> +	if (!IS_ERR_OR_NULL(port->usb_role_sw)) {
> +		of_platform_depopulate(&port->dev);
> +		usb_role_switch_unregister(port->usb_role_sw);
> +		cancel_work_sync(&port->usb_phy_work);
> +		usb_remove_phy(&port->usb_phy);
> +		port->usb_phy.dev->driver = NULL;
> +	}
> +

It's a bit difficult to tell what exactly changed because of the
additional move. The move looks correct because this is only valid for
USB2 ports, but I think it'd be easier to review if the move was done
prior to the addition of the ->driver clearing. Or perhaps a mention in
the commit message would be nice.

It's obviously up to Vinod and Kishon if they want to see this
clarified. Either way is fine with me, so:

Acked-by: Thierry Reding <treding@xxxxxxxxxx>

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