can: j1939: fix lockless local-destination check

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[ Upstream commit e4e8af62ad ]

j1939_priv.ents[].nusers is documented as protected by priv->lock, and
its updates already happen under that lock. j1939_can_recv() also reads
it under read_lock_bh(). However, j1939_session_skb_queue() and
j1939_tp_send() still read priv->ents[da].nusers without taking the
lock.

Those transport-side checks decide whether to set J1939_ECU_LOCAL_DST, so
they can race with j1939_local_ecu_get() and j1939_local_ecu_put() while
userspace is binding or releasing sockets concurrently with TP traffic.
This can misclassify TP/ETP sessions as local or remote and take the wrong
transport path.

Fix both transport paths by routing the destination-locality check through
a helper that reads ents[].nusers under read_lock_bh(&priv->lock).

Fixes: 9d71dd0c70 ("can: add support of SAE J1939 protocol")
Signed-off-by: Shuhao Fu <sfual@cse.ust.hk>
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/20260419140614.GA4041240@chcpu16
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Shuhao Fu 2026-05-07 10:22:26 +02:00 • committed by Greg Kroah-Hartman

parent 406141d506

commit 078ef8c95c

1 changed files with 14 additions and 4 deletions

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net/can/j1939/transport.c

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