Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 7eef18c0 authored by Oleksij Rempel's avatar Oleksij Rempel Committed by Greg Kroah-Hartman
Browse files

can: j1939: j1939_session_deactivate(): clarify lifetime of session object 

commit 0c71437dd50dd687c15d8ca80b3b68f10bb21d63 upstream.

The j1939_session_deactivate() is decrementing the session ref-count and
potentially can free() the session. This would cause use-after-free
situation.

However, the code calling j1939_session_deactivate() does always hold
another reference to the session, so that it would not be free()ed in
this code path.

This patch adds a comment to make this clear and a WARN_ON, to ensure
that future changes will not violate this requirement. Further this
patch avoids dereferencing the session pointer as a precaution to avoid
use-after-free if the session is actually free()ed.

Fixes: 9d71dd0c ("can: add support of SAE J1939 protocol")
Link: https://lore.kernel.org/r/20210714111602.24021-1-o.rempel@pengutronix.de


Reported-by: default avatarXiaochen Zou <xzou017@ucr.edu>
Signed-off-by: default avatarOleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 18b536de

net/can/j1939/transport.c

+7 −2
Original line number Diff line number Diff line
@@ -1075,11 +1075,16 @@ static bool j1939_session_deactivate_locked(struct j1939_session *session) 


static bool j1939_session_deactivate(struct j1939_session *session)

{

	struct j1939_priv *priv = session->priv;

	bool active;



	j1939_session_list_lock(session->priv);

	j1939_session_list_lock(priv);

	/* This function should be called with a session ref-count of at

	 * least 2.

	 */

	WARN_ON_ONCE(kref_read(&session->kref) < 2);

	active = j1939_session_deactivate_locked(session);

	j1939_session_list_unlock(session->priv);

	j1939_session_list_unlock(priv);



	return active;

}