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

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Date:   Mon, 8 May 2023 14:27:03 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Haotien Hsu <haotienh@...dia.com>, JC Kuo <jckuo@...dia.com>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        linux-phy@...ts.infradead.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, Wayne Chang <waynec@...dia.com>,
        EJ Hsu <ejh@...dia.com>
Subject: Re: [PATCH] phy: tegra: xusb: Fix use-after-free issue

On 04-05-23, 11:15, Thierry Reding wrote:
> On Thu, May 04, 2023 at 01:54:46PM +0800, Haotien Hsu wrote:
> > From: EJ Hsu <ejh@...dia.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@...r.kernel.org
> > 
> > Signed-off-by: EJ Hsu <ejh@...dia.com>
> > Signed-off-by: Haotien Hsu <haotienh@...dia.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:

I agree changes need to be clarified, expecting updated v2 :-)

> 
> Acked-by: Thierry Reding <treding@...dia.com>



-- 
~Vinod