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: 9d71dd0c7009 ("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 --- net/can/j1939/transport.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index fe3df23a2595..c6569f98d251 100644 --- a/net/can/j1939/transport.c +++ b/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; }