From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 7 Jul 2022 11:32:23 +0000 (+0200)
Subject: tty: n_gsm: fix missing corner cases in gsmld_poll()
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=447e0f4be8501664602eb2f433b689751cc6260d;p=linux.git

tty: n_gsm: fix missing corner cases in gsmld_poll()

[ Upstream commit 7e5b4322cde067e1d0f1bf8f490e93f664a7c843 ]

gsmld_poll() currently fails to handle the following corner cases correctly:
- remote party closed the associated tty

Add the missing checks and map those to EPOLLHUP.
Reorder the checks to group them by their reaction.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220707113223.3685-4-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 7a82fff7f5feb..b89655f585f14 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2954,12 +2954,15 @@ static __poll_t gsmld_poll(struct tty_struct *tty, struct file *file,
 
 	poll_wait(file, &tty->read_wait, wait);
 	poll_wait(file, &tty->write_wait, wait);
+
+	if (gsm->dead)
+		mask |= EPOLLHUP;
 	if (tty_hung_up_p(file))
 		mask |= EPOLLHUP;
+	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
+		mask |= EPOLLHUP;
 	if (!tty_is_writelocked(tty) && tty_write_room(tty) > 0)
 		mask |= EPOLLOUT | EPOLLWRNORM;
-	if (gsm->dead)
-		mask |= EPOLLHUP;
 	return mask;
 }