Re: [PATCH 4/4] tty: n_gsm: fix missing corner cases in gsmld_poll()

[Jiri Slaby]

On 06. 07. 22, 7:44, D. Starke wrote:
> From: Daniel Starke <daniel.starke@xxxxxxxxxxx>
>
> gsmld_poll() currently fails to handle some corner cases correctly:
> - tty ldisc association lost
> - 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@xxxxxxxxxxx>
> ---
>   drivers/tty/n_gsm.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> Based on tty-testing.
>
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 51447ccccbab..47566bd2ed6e 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -3051,14 +3051,20 @@ static __poll_t gsmld_poll(struct tty_struct *tty, struct file *file,
>   	__poll_t mask = 0;
>   	struct gsm_mux *gsm = tty->disc_data;
>   
> +	if (!gsm)
> +		return EPOLLHUP;

Hmm, how can this happen? It's a tty bug if it calls ld ops after 
NULLing disc_data.

thanks,
--
js
suse labs