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: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_tty.c

@@ -2228,6 +2228,16 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
 		}
 		__set_current_state(TASK_RUNNING);
 
+		if (ldata->icanon && !L_EXTPROC(tty)) {
+			retval = canon_copy_from_read_buf(tty, &b, &nr);
+			if (retval == -EAGAIN) {
+				retval = 0;
+				continue;
+			} else if (retval)
+				break;
+		} else {
+			int uncopied;
+
 			/* Deal with packet mode. */
 			if (packet && b == buf) {
 				if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
@@ -2238,15 +2248,6 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
 				nr--;
 			}
 
-		if (ldata->icanon && !L_EXTPROC(tty)) {
-			retval = canon_copy_from_read_buf(tty, &b, &nr);
-			if (retval == -EAGAIN) {
-				retval = 0;
-				continue;
-			} else if (retval)
-				break;
-		} else {
-			int uncopied;
 			/* The copy function takes the read lock and handles
 			   locking internally for this case */
 			uncopied = copy_from_read_buf(tty, &b, &nr);