[PATCH 5.18 0874/1095] tty: n_gsm: fix missing corner cases in gsmld_poll()

Greg Kroah-Hartman
2022-08-15T22:40:08Z

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

[ 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>
---
drivers/tty/n_gsm.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 7749de4f269a..3dd71ede4cd4 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -3057,12 +3057,15 @@ 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;
}

--
2.35.1