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-rw-r--r--drivers/tty/n_gsm.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 3778687f748b..0988aaaf2670 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2889,6 +2889,10 @@ static int gsmtty_install(struct tty_driver *driver, struct tty_struct *tty)
gsm = gsm_mux[mux];
if (gsm->dead)
return -EL2HLT;
+ /* If DLCI 0 is not yet fully open return an error. This is ok from a locking
+ perspective as we don't have to worry about this if DLCI0 is lost */
+ if (gsm->dlci[0] && gsm->dlci[0]->state != DLCI_OPEN)
+ return -EL2NSYNC;
dlci = gsm->dlci[line];
if (dlci == NULL) {
alloc = true;