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

Thierry Reding
2023-05-04T09:15:48Z

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On Thu, May 04, 2023 at 01:54:46PM +0800, Haotien Hsu wrote:
> From: EJ Hsu <ejh@nvidia.com>
>
> 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@vger.kernel.org
>
> Signed-off-by: EJ Hsu <ejh@nvidia.com>
> Signed-off-by: Haotien Hsu <haotienh@nvidia.com>
> ---
> 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@nvidia.com>

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