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Subject[PATCH 1/1] usb: gadget: Don't attempt to dequeue requests for a disabled USB endpoint on Freescale hardware
Date
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.

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 requests.

Signed-off-by: Simon Haggett <simon.haggett@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 b/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;

spin_lock_irqsave(&ep->udc->lock, flags);
--
1.7.4.1


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