[PATCH 1/1] usb: gadget: Don't attempt to dequeue requests for a disabled USB endpoint on Freescale hardware
simon.haggett at realvnc.com
Mon Oct 22 22:49:51 EST 2012
On 22/10/12 11:47, Laurent Pinchart wrote:
> On Monday 22 October 2012 03:33:19 Li Yang-R58472 wrote:
>> On Saturday, October 20, 2012 1:37 AM Felipe Balbi wrote:
>>> On Fri, Oct 19, 2012 at 06:19:26PM +0100, Simon Haggett wrote:
>>>> Some gadget drivers may attempt to dequeue requests for an endpoint
>>>> that has already been disabled. For example, in the UVC gadget driver,
>>>> uvc_function_set_alt() will call usb_ep_disable() when alt setting 0
>>>> is selected. When the userspace application subsequently issues the
>>>> VIDIOC_STREAMOFF ioctl, uvc_video_enable() invokes usb_ep_dequeue() to
>>> ensure that all requests have been cancelled.
>>> bug is on uvc gadget, then. Laurent ?
> We've discussed this topic a couple of months before. I believe that's not a
>>> Also, fsl should be removed from the tree, I'm trying to persuade iMX
>>> folks to use drivers/usb/chipidea instead.
>> Besides the iMX usage, the driver is also being used by many Freescale
>> PowerPC/Coldfire SoCs. I agree that it's ideal to move to a common driver.
>> But it is a large task to make the chipidea driver works for all the
>> hardware that fsl_udc had supported and been tested on.
>>>> For the Freescale High Speed Dual-Role USB controller,
>>>> fsl_ep_dequeue() provides the implementation of usb_ep_dequeue(). If
>>>> this is called for a disabled endpoint, a kernel oops will occur when
>>> the ep->ep.desc field is dereferenced (by ep_index()).
>>>> fsl_ep_disable() sets this field to NULL, as well as deleting all
>>>> pending requests for the endpoint.
>>>> This patch adds an additional check to fsl_ep_dequeue() to ensure that
>>>> the endpoint has not already been disabled before attempting to dequeue
>>>> Signed-off-by: Simon Haggett <simon.haggett at realvnc.com>
>>>> drivers/usb/gadget/fsl_udc_core.c | 5 ++++-
>>>> 1 files changed, 4 insertions(+), 1 deletions(-)
>>>> diff --git a/drivers/usb/gadget/fsl_udc_core.c
>>>> index 6ae70cb..acd513b 100644
>>>> --- a/drivers/usb/gadget/fsl_udc_core.c
>>>> +++ b/drivers/usb/gadget/fsl_udc_core.c
>>>> @@ -955,7 +955,10 @@ static int fsl_ep_dequeue(struct usb_ep *_ep,
>>> struct usb_request *_req)
>>>> int ep_num, stopped, ret = 0;
>>>> u32 epctrl;
>>>> - if (!_ep || !_req)
>>>> + /* Ensure that the ep and request are valid, and the ep is not
>>>> + * disabled
>>>> + */
>>>> + if (!_ep || !_req || !ep->ep.desc)
>>>> return -EINVAL;
> Shouldn't that last check be done with a lock taken ?
I had presumed a lock wasn't necessary because ep->ep.desc is only set
to NULL by fsl_ep_disable() which, since it is called by
usb_ep_disable(), should only be invoked when no other task is using the
endpoint (according to include/linux/usb/gadget.h). Furthermore, the
chipidea UDC driver does check the equivalent of this field is not NULL
without taking a lock (ep_dequeue() in drivers/usb/chipidea/udc.c).
However, it is possible that I'm misunderstanding something here, so
apologies if I am.
>>>> spin_lock_irqsave(&ep->udc->lock, flags);
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