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


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