net: can: j1939: enhanced error handling for tightly received RTS mes…

…sages in xtp_rx_rts_session_new

This patch enhances error handling in scenarios with RTS (Request to
Send) messages arriving closely. It replaces the less informative WARN_ON_ONCE
backtraces with a new error handling method. This provides clearer error
messages and allows for the early termination of problematic sessions.
Previously, sessions were only released at the end of j1939_xtp_rx_rts().

Potentially this could be reproduced with something like:
testj1939 -r vcan0:0x80 &
while true; do
	# send first RTS
	cansend vcan0 18EC8090#1014000303002301;
	# send second RTS
	cansend vcan0 18EC8090#1014000303002301;
	# send abort
	cansend vcan0 18EC8090#ff00000000002301;
done

Fixes: 9d71dd0 ("can: add support of SAE J1939 protocol")
Reported-by: syzbot+daa36413a5cedf799ae4@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/all/20231117124959.961171-1-o.rempel@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/j1939/transport.c

@@ -1593,8 +1593,8 @@ j1939_session *j1939_xtp_rx_rts_session_new(struct j1939_priv *priv,
  struct j1939_sk_buff_cb skcb = *j1939_skb_to_cb(skb);
  struct j1939_session *session;
  const u8 *dat;
+ int len, ret;
  pgn_t pgn;
- int len;
 
  netdev_dbg(priv->ndev, "%s\n", __func__);
 
@@ -1653,7 +1653,22 @@ j1939_session *j1939_xtp_rx_rts_session_new(struct j1939_priv *priv,
  session->tskey = priv->rx_tskey++;
  j1939_sk_errqueue(session, J1939_ERRQUEUE_RX_RTS);
 
- WARN_ON_ONCE(j1939_session_activate(session));
+ ret = j1939_session_activate(session);
+ if (ret) {
+ /* Entering this scope indicates an issue with the J1939 bus.
+ * Possible scenarios include:
+ * - A time lapse occurred, and a new session was initiated
+ * due to another packet being sent correctly. This could
+ * have been caused by too long interrupt, debugger, or being
+ * out-scheduled by another task.
+ * - The bus is receiving numerous erroneous packets, either
+ * from a malfunctioning device or during a test scenario.
+ */
+ netdev_alert(priv->ndev, "%s: 0x%p: concurrent session with same addr (%02x %02x) is already active.\n",
+ __func__, session, skcb.addr.sa, skcb.addr.da);
+ j1939_session_put(session);
+ return NULL;
+ }
 
  return session;
 }