media: streamzap: prevent processing IR data on URB failure

If streamzap_callback() receives an urb with any non-critical error
status, i.e. any error code other than -ECONNRESET, -ENOENT or -ESHUTDOWN,
it will try to process IR data, ignoring a possible transfer failure.

Make streamzap_callback() process IR data only when urb->status is 0.
Move processing logic to a separate function to make code cleaner and
more similar to the URB completion handlers in other RC drivers.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 19770693c354 ("V4L/DVB: staging/lirc: add lirc_streamzap driver")
Cc: [e-mail]
Signed-off-by: Murad Masimov <[e-mail]>
Signed-off-by: Sean Young <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>

drivers/media/rc/streamzap.c

···
 	sz_push_full_space(sz, value & SZ_SPACE_MASK);
 }
 
-/*
- * streamzap_callback - usb IRQ handler callback
- *
- * This procedure is invoked on reception of data from
- * the usb remote.
- */
-static void streamzap_callback(struct urb *urb)
+static void sz_process_ir_data(struct streamzap_ir *sz, int len)
 {
-	struct streamzap_ir *sz;
 	unsigned int i;
-	int len;
 
-	if (!urb)
-		return;
-
-	sz = urb->context;
-	len = urb->actual_length;
-
-	switch (urb->status) {
-	case -ECONNRESET:
-	case -ENOENT:
-	case -ESHUTDOWN:
-		/*
-		 * this urb is terminated, clean up.
-		 * sz might already be invalid at this point
-		 */
-		dev_err(sz->dev, "urb terminated, status: %d\n", urb->status);
-		return;
-	default:
-		break;
-	}
-
-	dev_dbg(sz->dev, "%s: received urb, len %d\n", __func__, len);
 	for (i = 0; i < len; i++) {
 		dev_dbg(sz->dev, "sz->buf_in[%d]: %x\n",
 			i, (unsigned char)sz->buf_in[i]);
···
 	}
 
 	ir_raw_event_handle(sz->rdev);
+}
+
+/*
+ * streamzap_callback - usb IRQ handler callback
+ *
+ * This procedure is invoked on reception of data from
+ * the usb remote.
+ */
+static void streamzap_callback(struct urb *urb)
+{
+	struct streamzap_ir *sz;
+	int len;
+
+	if (!urb)
+		return;
+
+	sz = urb->context;
+	len = urb->actual_length;
+
+	switch (urb->status) {
+	case 0:
+		dev_dbg(sz->dev, "%s: received urb, len %d\n", __func__, len);
+		sz_process_ir_data(sz, len);
+		break;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+		/*
+		 * this urb is terminated, clean up.
+		 * sz might already be invalid at this point
+		 */
+		dev_err(sz->dev, "urb terminated, status: %d\n", urb->status);
+		return;
+	default:
+		break;
+	}
+
 	usb_submit_urb(urb, GFP_ATOMIC);
 }