This is a note to let you know that I've just added the patch titled
can: isotp: isotp_ops: fix poll() to not report false EPOLLOUT events
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
can-isotp-isotp_ops-fix-poll-to-not-report-false-epollout-events.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 79e19fa79cb5d5f1b3bf3e3ae24989ccb93c7b7b Mon Sep 17 00:00:00 2001
From: Michal Sojka <michal.sojka@xxxxxxx>
Date: Fri, 31 Mar 2023 14:55:11 +0200
Subject: can: isotp: isotp_ops: fix poll() to not report false EPOLLOUT events
From: Michal Sojka <michal.sojka@xxxxxxx>
commit 79e19fa79cb5d5f1b3bf3e3ae24989ccb93c7b7b upstream.
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@xxxxxxx
v1: https://lore.kernel.org/all/20230224010659.48420-1-michal.sojka@xxxxxxx
https://lore.kernel.org/all/b53a04a2-ba1f-3858-84c1-d3eb3301ae15@xxxxxxxxxxxx
Signed-off-by: Michal Sojka <michal.sojka@xxxxxxx>
Reported-by: Jakub Jira <jirajak2@xxxxxxxxxxx>
Tested-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
Acked-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol")
Link: https://lore.kernel.org/all/20230331125511.372783-1-michal.sojka@xxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/can/isotp.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1615,6 +1615,21 @@ 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)
{
@@ -1630,7 +1645,7 @@ 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,
Patches currently in stable-queue which might be from michal.sojka@xxxxxxx are
queue-6.2/can-isotp-isotp_ops-fix-poll-to-not-report-false-epollout-events.patch
