linux-kernel - [PATCH 10/20] tty: n_gsm: fix missing explicit ldisc flush

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Date:   Thu, 14 Apr 2022 02:42:15 -0700
From:   "D. Starke" <daniel.starke@...mens.com>
To:     linux-serial@...r.kernel.org, gregkh@...uxfoundation.org,
        jirislaby@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Daniel Starke <daniel.starke@...mens.com>
Subject: [PATCH 10/20] tty: n_gsm: fix missing explicit ldisc flush

From: Daniel Starke <daniel.starke@...mens.com>

In gsm_cleanup_mux() the muxer is closed down and all queues are removed.
However, removing the queues is done without explicit control of the
underlying buffers. Flush those before freeing up our queues to ensure
that all outgoing queues are cleared consistently. Otherwise, a new mux
connection establishment attempt may time out while the underlying tty is
still busy sending out the remaining data from the previous connection.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@...r.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
---
 drivers/tty/n_gsm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 6b953dfbb155..1430d7f83bd2 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2152,6 +2152,7 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 			gsm_dlci_release(gsm->dlci[i]);
 	mutex_unlock(&gsm->mutex);
 	/* Now wipe the queues */
+	tty_ldisc_flush(gsm->tty);
 	list_for_each_entry_safe(txq, ntxq, &gsm->tx_list, list)
 		kfree(txq);
 	INIT_LIST_HEAD(&gsm->tx_list);
-- 
2.25.1