From: Oleksij Rempel <o.rempel@pengutronix.de> stable inclusion from stable-5.10.56 commit 55dd22c5d029423f513fd849e633adf0e9c10d0c bugzilla: 176004 https://gitee.com/openeuler/kernel/issues/I4DYZ4 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- 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: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") Link: https://lore.kernel.org/r/20210714111602.24021-1-o.rempel@pengutronix.de Reported-by: Xiaochen Zou <xzou017@ucr.edu> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Chen Jun <chenjun102@huawei.com> Acked-by: Weilong Chen <chenweilong@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- net/can/j1939/transport.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index 411322976950..bdc95bd7a851 100644 --- a/net/can/j1939/transport.c +++ b/net/can/j1939/transport.c @@ -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; } -- 2.20.1