[media] usbtv: don't do DMA on stack

As reported by smatch:
	drivers/media/usb/usbtv/usbtv-video.c:716 usbtv_s_ctrl() error: doing dma on the stack (data)
	drivers/media/usb/usbtv/usbtv-video.c:758 usbtv_s_ctrl() error: doing dma on the stack (data)

We should not do it, as it won't work on Kernels 4.9 and upper.
So, alloc a buffer for it.

Fixes: c53a846c48f2 ("[media] usbtv: add video controls")
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

diff --git a/drivers/media/usb/usbtv/usbtv-video.c b/drivers/media/usb/usbtv/usbtv-video.c
index 86ffbf8..d3b6d3d 100644 (file)
--- a/drivers/media/usb/usbtv/usbtv-video.c
+++ b/drivers/media/usb/usbtv/usbtv-video.c
@@ -704,10 +704,14 @@ static int usbtv_s_ctrl(struct v4l2_ctrl *ctrl)
 {
        struct usbtv *usbtv = container_of(ctrl->handler, struct usbtv,
                                                                ctrl);
-       u8 data[3];
+       u8 *data;
        u16 index, size;
        int ret;
 
+       data = kmalloc(3, GFP_KERNEL);
+       if (!data)
+               return -ENOMEM;
+
        /*
         * Read in the current brightness/contrast registers. We need them
         * both, because the values are for some reason interleaved.
@@ -717,6 +721,8 @@ static int usbtv_s_ctrl(struct v4l2_ctrl *ctrl)
                        usb_sndctrlpipe(usbtv->udev, 0), USBTV_CONTROL_REG,
                        USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
                        0, USBTV_BASE + 0x0244, (void *)data, 3, 0);
+               if (ret < 0)
+                       goto error;
        }
 
        switch (ctrl->id) {
@@ -752,6 +758,7 @@ static int usbtv_s_ctrl(struct v4l2_ctrl *ctrl)
                }
                break;
        default:
+               kfree(data);
                return -EINVAL;
        }
 
@@ -759,12 +766,13 @@ static int usbtv_s_ctrl(struct v4l2_ctrl *ctrl)
                        USBTV_CONTROL_REG,
                        USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
                        0, index, (void *)data, size, 0);
-       if (ret < 0) {
+
+error:
+       if (ret < 0)
                dev_warn(usbtv->dev, "Failed to submit a control request.\n");
-               return ret;
-       }
 
-       return 0;
+       kfree(data);
+       return ret;
 }
 
 static const struct v4l2_ctrl_ops usbtv_ctrl_ops = {