tty: n_gsm: fix packet re-transmission without open control channel

[ Upstream commit 4fae831b3a71fc5a44cc5c7d0b8c1267ee7659f5 ]

In the current implementation control packets are re-transmitted even if
the control channel closed down during T2. This is wrong.
Check whether the control channel is open before re-transmitting any
packets. Note that control channel open/close is handled by T1 and not T2
and remains unaffected by this.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220701061652.39604-7-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 56a3466..3f65990 100644 (file)
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1546,7 +1546,7 @@ static void gsm_control_retransmit(struct timer_list *t)
        spin_lock_irqsave(&gsm->control_lock, flags);
        ctrl = gsm->pending_cmd;
        if (ctrl) {
-               if (gsm->cretries == 0) {
+               if (gsm->cretries == 0 || !gsm->dlci[0] || gsm->dlci[0]->dead) {
                        gsm->pending_cmd = NULL;
                        ctrl->error = -ETIMEDOUT;
                        ctrl->done = 1;