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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Oliver Hartkopp <socketcan@hartkopp.net>,
        Marc Kleine-Budde <mkl@pengutronix.de>
Subject: [PATCH 4.14 020/315] can: gw: synchronize rcu operations before removing gw job entry
Date:   Mon, 19 Jul 2021 16:48:29 +0200
Message-Id: <20210719144943.547552268@linuxfoundation.org>
In-Reply-To: <20210719144942.861561397@linuxfoundation.org>
References: <20210719144942.861561397@linuxfoundation.org>
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From: Oliver Hartkopp <socketcan@hartkopp.net>

commit fb8696ab14adadb2e3f6c17c18ed26b3ecd96691 upstream.

can_can_gw_rcv() is called under RCU protection, so after calling
can_rx_unregister(), we have to call synchronize_rcu in order to wait
for any RCU read-side critical sections to finish before removing the
kmem_cache entry with the referenced gw job entry.

Link: https://lore.kernel.org/r/20210618173645.2238-1-socketcan@hartkopp.net
Fixes: c1aabdf379bc ("can-gw: add netlink based CAN routing")
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/can/gw.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -494,6 +494,7 @@ static int cgw_notifier(struct notifier_
 			if (gwj->src.dev == dev || gwj->dst.dev == dev) {
 				hlist_del(&gwj->list);
 				cgw_unregister_filter(net, gwj);
+				synchronize_rcu();
 				kmem_cache_free(cgw_cache, gwj);
 			}
 		}
@@ -941,6 +942,7 @@ static void cgw_remove_all_jobs(struct n
 	hlist_for_each_entry_safe(gwj, nx, &net->can.cgw_list, list) {
 		hlist_del(&gwj->list);
 		cgw_unregister_filter(net, gwj);
+		synchronize_rcu();
 		kmem_cache_free(cgw_cache, gwj);
 	}
 }
@@ -1010,6 +1012,7 @@ static int cgw_remove_job(struct sk_buff
 
 		hlist_del(&gwj->list);
 		cgw_unregister_filter(net, gwj);
+		synchronize_rcu();
 		kmem_cache_free(cgw_cache, gwj);
 		err = 0;
 		break;