We should warn user-space that it is doing something wrong when trying to
activate sessions with identical parameters but WARN_ON_ONCE macro can not
be used here as it serves a different purpose.

So it would be good to replace it with netdev_warn_once() message.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Signed-off-by: Fedor Pchelkin <redacted>
Signed-off-by: Alexey Khoroshilov <redacted>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
v1 -> v2: Used netdev_warn_once() instead of pr_warn_once()

 net/can/j1939/socket.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index f5ecfdcf57b2..09e1d78bd22c 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c

@@ -178,7 +178,10 @@ 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)) {
+		netdev_warn_once(first->priv->ndev,
+						 "%s: 0x%p: Identical session is already activated.\n",
+						 __func__, first);
 		first->err = -EBUSY;
 		goto activate_next;
 	} else {

-- 
2.25.1