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authorOleksij Rempel <o.rempel@pengutronix.de>2021-07-14 13:16:02 +0200
committerMarc Kleine-Budde <mkl@pengutronix.de>2021-07-24 19:01:53 +0200
commit0c71437dd50dd687c15d8ca80b3b68f10bb21d63 (patch)
tree09d4b62306d47a94ec7d5d71fee72f3fb0ec7e8f /net/can
parent54f93336d000229f72c26d8a3f69dd256b744528 (diff)
can: j1939: j1939_session_deactivate(): clarify lifetime of session object
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>
Diffstat (limited to 'net/can')
-rw-r--r--net/can/j1939/transport.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index c3946c355882..bb1092c3e7e3 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;
}