[PATCH] tty: fix memory leak in gsm_activate_mux

[Edward AD]

When the call to gsm_register_devices() fails, we need to reclaim the memory
requested in gsm_dlci_alloc().

Fixes: 01aecd917114 ("tty: n_gsm: fix tty registration before control channel open")
Reported-and-tested-by: syzbot+b5d1f455d385b2c7da3c@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Edward AD <twuufnxlz@xxxxxxxxx>
---
 drivers/tty/n_gsm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index b3550ff9c494..df9bb87652b0 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -3136,8 +3136,10 @@ static int gsm_activate_mux(struct gsm_mux *gsm)
 		gsm->receive = gsm1_receive;
 
 	ret = gsm_register_devices(gsm_tty_driver, gsm->num);
-	if (ret)
+	if (ret) {
+		gsm_dlci_free(&dlci->port);
 		return ret;
+	}
 
 	gsm->has_devices = true;
 	gsm->dead = false;		/* Tty opens are now permissible */
-- 
2.25.1