n_tty: Fix stale echo output

When echoes cannot be flushed to output (usually because the tty
has no more write room) and L_ECHO is subsequently turned off, then
when L_ECHO is turned back on, stale echoes are output.

Output completed echoes regardless of the L_ECHO setting:
  1. before normal writes to that tty
  2. if the tty was stopped by soft flow control and is being
     restarted

Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: <stable@vger.kernel.org> # 3.13.x
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 2747a3b20a50b31a621c137bcdef3dd826dcdd77..d15624c1b75161877e6319e6460981866feb54cb 100644 (file)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -817,8 +817,7 @@ static void process_echoes(struct tty_struct *tty)
        struct n_tty_data *ldata = tty->disc_data;
        size_t echoed;
 
-       if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
-           ldata->echo_mark == ldata->echo_tail)
+       if (ldata->echo_mark == ldata->echo_tail)
                return;
 
        mutex_lock(&ldata->output_lock);
@@ -1244,7 +1243,8 @@ n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
        if (L_ECHO(tty)) {
                echo_char(c, tty);
                commit_echoes(tty);
-       }
+       } else
+               process_echoes(tty);
        isig(signal, tty);
        return;
 }
@@ -1274,7 +1274,7 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
        if (I_IXON(tty)) {
                if (c == START_CHAR(tty)) {
                        start_tty(tty);
-                       commit_echoes(tty);
+                       process_echoes(tty);
                        return 0;
                }
                if (c == STOP_CHAR(tty)) {
@@ -1820,8 +1820,10 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
         * Fix tty hang when I_IXON(tty) is cleared, but the tty
         * been stopped by STOP_CHAR(tty) before it.
         */
-       if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped)
+       if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
                start_tty(tty);
+               process_echoes(tty);
+       }
 
        /* The termios change make the tty ready for I/O */
        if (waitqueue_active(&tty->write_wait))