linux-kernel - Re: [PATCH v2] char: xillybus: Check endpoint type before allocing

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Message-ID: <627FA604.2010302@gmail.com>
Date:   Sat, 14 May 2022 15:52:20 +0300
From:   Eli Billauer <eli.billauer@...il.com>
To:     Zheyu Ma <zheyuma97@...il.com>
CC:     arnd@...db.de, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] char: xillybus: Check endpoint type before allocing

On 14/05/22 14:48, Zheyu Ma wrote:
> The driver submits bulk urb without checking the endpoint type is
> actually bulk.
>
> [    3.108690] usb 1-1: BOGUS urb xfer, pipe 3 != type 1
> [    3.108983] WARNING: CPU: 0 PID: 211 at drivers/usb/core/urb.c:503 usb_submit_urb+0xcd9/0x18b0
> [    3.110976] RIP: 0010:usb_submit_urb+0xcd9/0x18b0
> [    3.115318] Call Trace:
> [    3.115452]<TASK>
> [    3.115570]  try_queue_bulk_in+0x43c/0x6e0 [xillyusb]
> [    3.115838]  xillyusb_probe+0x488/0x1230 [xillyusb]
>
> Add a check in endpoint_alloc() to fix the bug.
>
> Signed-off-by: Zheyu Ma<zheyuma97@...il.com>
> ---
> Changes in v2:
>      - Check the endpoint type at probe time
> ---
>   drivers/char/xillybus/xillyusb.c | 27 ++++++++++++++++++++++++++-
>   1 file changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/xillybus/xillyusb.c b/drivers/char/xillybus/xillyusb.c
> index dc3551796e5e..4467f13993ef 100644
> --- a/drivers/char/xillybus/xillyusb.c
> +++ b/drivers/char/xillybus/xillyusb.c
> @@ -167,6 +167,7 @@ struct xillyusb_dev {
>   	struct device		*dev; /* For dev_err() and such */
>   	struct kref		kref;
>   	struct workqueue_struct	*workq;
> +	struct usb_interface *intf;
>
>   	int error;
>   	spinlock_t error_lock; /* protect @error */
> @@ -475,6 +476,25 @@ static void endpoint_dealloc(struct xillyusb_endpoint *ep)
>   	kfree(ep);
>   }
>
> +static int xillyusb_check_endpoint(struct xillyusb_dev *xdev, u8 ep_num)
> +{
> +	struct usb_host_interface *if_desc = xdev->intf->altsetting;
> +	int i;
> +
> +	for (i = 0; i<  if_desc->desc.bNumEndpoints; i++) {
> +		struct usb_endpoint_descriptor *ep =&if_desc->endpoint[i].desc;
> +
> +		if (ep->bEndpointAddress != ep_num)
> +			continue;
> +
> +		if ((usb_pipein(ep_num)&&  usb_endpoint_is_bulk_in(ep)) ||
> +			(usb_pipeout(ep_num)&&  usb_endpoint_is_bulk_out(ep)))
> +			return 0;
> +	}
> +
> +	return -EINVAL;
> +}
> +
>   static struct xillyusb_endpoint
>   *endpoint_alloc(struct xillyusb_dev *xdev,
>   		u8 ep_num,
> @@ -482,10 +502,14 @@ static struct xillyusb_endpoint
>   		unsigned int order,
>   		int bufnum)
>   {
> -	int i;
> +	int i, ret;
>
>   	struct xillyusb_endpoint *ep;
>
> +	ret = xillyusb_check_endpoint(xdev, ep_num);
> +	if (ret)
> +		return NULL;
> +
>   	ep = kzalloc(sizeof(*ep), GFP_KERNEL);
>
>   	if (!ep)
> @@ -2125,6 +2149,7 @@ static int xillyusb_probe(struct usb_interface *interface,
>   	mutex_init(&xdev->process_in_mutex);
>   	mutex_init(&xdev->msg_mutex);
>
> +	xdev->intf = interface;
>   	xdev->udev = usb_get_dev(interface_to_usbdev(interface));
>   	xdev->dev =&interface->dev;
>   	xdev->error = 0;
>    
I wonder why this check is necessary. The XillyUSB device presents bulk 
endpoints only, and the driver never tries anything else.

Actually, if this warning appears in a real-life scenario, it definitely 
indicates a serious problem. So I think the warning should be visible, 
rather than silenced like this.

I realize that a code sanitizer has been triggered, but is there more to 
this?

Thanks,
   Eli