[PATCH] usb: gadget: uvc: clamp SEND_RESPONSE length to the response buffer

[Muhammad Bilal <meatuni001@gmail.com>]

uvc_send_response() builds the UVC control response from a user-supplied
struct uvc_request_data:

	req->length = min_t(unsigned int, uvc->event_length, data->length);
	...
	memcpy(req->buf, data->data, req->length);

req->length is clamped to uvc->event_length, which is taken from the
host control request wLength (up to UVC_MAX_REQUEST_SIZE, 64), and to
data->length, which comes from the UVCIOC_SEND_RESPONSE ioctl and is
only checked for being negative.  The source buffer data->data is only
60 bytes, so a response with uvc->event_length and data->length both
greater than 60 makes memcpy() read past the end of data->data.

Clamp req->length to sizeof(data->data) as well.

Fixes: a5eaaa1f33e7 ("usb: gadget: uvc: use capped length value")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
---
 drivers/usb/gadget/function/uvc_v4l2.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c
index 514e5930b9ca9..dfa0521a243ac 100644
--- a/drivers/usb/gadget/function/uvc_v4l2.c
+++ b/drivers/usb/gadget/function/uvc_v4l2.c
@@ -200,6 +200,8 @@ uvc_send_response(struct uvc_device *uvc, struct uvc_request_data *data)
 		return usb_ep_set_halt(cdev->gadget->ep0);
 
 	req->length = min_t(unsigned int, uvc->event_length, data->length);
+	if (req->length > sizeof(data->data))
+		req->length = sizeof(data->data);
 	req->zero = data->length < uvc->event_length;
 
 	memcpy(req->buf, data->data, req->length);
-- 
2.54.0