Re: [PATCH] usb: gadget: raw_gadget: fix dangling ep->desc on enable failure

[Andrey Konovalov]

On Tue, Oct 27, 2026 at 4:23 AM Liu Chao <liuc63@xxxxxxxxxxxx> wrote:
>
> raw_ioctl_ep_enable() assigns the user-supplied endpoint descriptor
> to ep->ep->desc before calling usb_ep_enable(). If usb_ep_enable()
> fails, or if the subsequent usb_ep_alloc_request() fails, the error
> path frees desc via out_free but leaves ep->ep->desc pointing at the
> freed memory.
>
> The UDC driver may have captured the stale descriptor pointer during
> the partial enable sequence and may dereference it in subsequent
> operations, resulting in a use-after-free.
>
> Clear ep->ep->desc before jumping to out_free on both failure paths
> so the pointer never outlives the descriptor it references.
>
> Fixes: 97df5e5758f7 ("usb: raw-gadget: fix gadget endpoint selection")
> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Guanglei Zhu <zhugl3@xxxxxxxxxxxx>
> Signed-off-by: Liu Chao <liuc63@xxxxxxxxxxxx>
> ---
>  drivers/usb/gadget/legacy/raw_gadget.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/usb/gadget/legacy/raw_gadget.c b/drivers/usb/gadget/legacy/raw_gadget.c
> index 46f343ba4..b52ab3ce7 100644
> --- a/drivers/usb/gadget/legacy/raw_gadget.c
> +++ b/drivers/usb/gadget/legacy/raw_gadget.c
> @@ -886,6 +886,7 @@ static int raw_ioctl_ep_enable(struct raw_dev *dev, unsigned long value)
>                 if (ret < 0) {
>                         dev_err(&dev->gadget->dev,
>                                 "fail, usb_ep_enable returned %d\n", ret);
> +                       ep->ep->desc = NULL;
>                         goto out_free;
>                 }
>                 ep->req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC);
> @@ -893,6 +894,7 @@ static int raw_ioctl_ep_enable(struct raw_dev *dev, unsigned long value)
>                         dev_err(&dev->gadget->dev,
>                                 "fail, usb_ep_alloc_request failed\n");
>                         usb_ep_disable(ep->ep);
> +                       ep->ep->desc = NULL;
>                         ret = -ENOMEM;
>                         goto out_free;
>                 }
> --
> 2.50.1
>

Commit message should ideally mention that the use-after-free is not
actually reachable.

But the clean-up makes sense:

Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>