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

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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: Michal Sojka <michal.sojka@cvut.cz>
Reported-by: Jakub Jira <jirajak2@fel.cvut.cz>
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Fixes: e057dd3fc2 ("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: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Michal Sojka 2023-03-31 14:55:11 +02:00 committed by Marc Kleine-Budde
parent 0145462fc8
commit 79e19fa79c
1 changed files with 16 additions and 1 deletions
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17
net/can/isotp.c
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@ -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,