Commit 79e19fa7 authored by Michal Sojka's avatar Michal Sojka Committed by Marc Kleine-Budde
Browse files

can: isotp: isotp_ops: fix poll() to not report false EPOLLOUT events 

When using select()/poll()/epoll() with a non-blocking ISOTP socket to
wait for when non-blocking write is possible, a false EPOLLOUT event
is sometimes returned. This can happen at least after sending a
message which must be split to multiple CAN frames.

The reason is that isotp_sendmsg() returns -EAGAIN when tx.state is
not equal to ISOTP_IDLE and this behavior is not reflected in
datagram_poll(), which is used in isotp_ops.

This is fixed by introducing ISOTP-specific poll function, which
suppresses the EPOLLOUT events in that case.

v2: https://lore.kernel.org/all/20230302092812.320643-1-michal.sojka@cvut.cz
v1: https://lore.kernel.org/all/20230224010659.48420-1-michal.sojka@cvut.cz
    https://lore.kernel.org/all/b53a04a2-ba1f-3858-84c1-d3eb3301ae15@hartkopp.net



Signed-off-by: default avatarMichal Sojka <michal.sojka@cvut.cz>
Reported-by: default avatarJakub Jira <jirajak2@fel.cvut.cz>
Tested-by: default avatarOliver Hartkopp <socketcan@hartkopp.net>
Acked-by: default avatarOliver Hartkopp <socketcan@hartkopp.net>
Fixes: e057dd3f ("can: add ISO 15765-2:2016 transport protocol")
Link: https://lore.kernel.org/all/20230331125511.372783-1-michal.sojka@cvut.cz


Cc: stable@vger.kernel.org
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent 0145462f

net/can/isotp.c

+16 −1
Original line number Diff line number Diff line
@@ -1608,6 +1608,21 @@ static int isotp_init(struct sock *sk) 
	return 0;

}



static __poll_t isotp_poll(struct file *file, struct socket *sock, poll_table *wait)

{

	struct sock *sk = sock->sk;

	struct isotp_sock *so = isotp_sk(sk);



	__poll_t mask = datagram_poll(file, sock, wait);

	poll_wait(file, &so->wait, wait);



	/* Check for false positives due to TX state */

	if ((mask & EPOLLWRNORM) && (so->tx.state != ISOTP_IDLE))

		mask &= ~(EPOLLOUT | EPOLLWRNORM);



	return mask;

}



static int isotp_sock_no_ioctlcmd(struct socket *sock, unsigned int cmd,

				  unsigned long arg)

{
@@ -1623,7 +1638,7 @@ static const struct proto_ops isotp_ops = { 
	.socketpair = sock_no_socketpair,

	.accept = sock_no_accept,

	.getname = isotp_getname,

	.poll = datagram_poll,

	.poll = isotp_poll,

	.ioctl = isotp_sock_no_ioctlcmd,

	.gettstamp = sock_gettstamp,

	.listen = sock_no_listen,