n_tty: Only process packet mode data in raw mode

Packet mode can only be set for a pty master, and a pty master is
always in raw mode since its termios cannot be changed.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Reviewed-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_tty.c

@@ -2228,16 +2228,6 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
 		}
 		__set_current_state(TASK_RUNNING);
 
-		/* Deal with packet mode. */
-		if (packet && b == buf) {
-			if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
-				retval = -EFAULT;
-				b--;
-				break;
-			}
-			nr--;
-		}
-
 		if (ldata->icanon && !L_EXTPROC(tty)) {
 			retval = canon_copy_from_read_buf(tty, &b, &nr);
 			if (retval == -EAGAIN) {
@@ -2247,6 +2237,17 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
 				break;
 		} else {
 			int uncopied;
+
+			/* Deal with packet mode. */
+			if (packet && b == buf) {
+				if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
+					retval = -EFAULT;
+					b--;
+					break;
+				}
+				nr--;
+			}
+
 			/* The copy function takes the read lock and handles
 			   locking internally for this case */
 			uncopied = copy_from_read_buf(tty, &b, &nr);