Hi Fedor,
On Wed, Jul 20, 2022 at 02:06:45PM +0300, Fedor Pchelkin wrote:
> The purpose of WARN_ON_ONCE if the session with the same parameters
> has already been activated and is currently in active_session_list is
> not very clear. Is this warning implemented to indicate that userspace
> is doing something wrong?
yes.
> As far as I can see, there are two lists: active_session_list (which
> is for the whole device) and sk_session_queue (which is unique for
> each j1939_sock), and the situation when we have two sessions with
> the same type, addresses and destinations in two different
> sk_session_queues (owned by two different sockets) is actually highly
> probable - one is active and the other is willing to become active
> but the j1939_session_activate() does not let that happen. It is
> correct behaviour as I assume.
No. It is not typical use case and most probably it will create
problems. Are you working on some system where this use case is valid?
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
>
> Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
> Signed-off-by: Fedor Pchelkin <pchelkin@xxxxxxxxx>
> Signed-off-by: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
>
> ---
> net/can/j1939/socket.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
> index f5ecfdcf57b2..be4b73afa16c 100644
> --- a/net/can/j1939/socket.c
> +++ b/net/can/j1939/socket.c
> @@ -178,7 +178,7 @@ static void j1939_sk_queue_activate_next_locked(struct j1939_session *session)
> if (!first)
> return;
>
> - if (WARN_ON_ONCE(j1939_session_activate(first))) {
> + if (j1939_session_activate(first)) {
> first->err = -EBUSY;
> goto activate_next;
> } else {
> --
> 2.25.1
>
>
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