[PATCH 5.12 058/700] can: gw: synchronize rcu operations before removing gw job entry

[Greg Kroah-Hartman]

From: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>

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@xxxxxxxxxxxx
Fixes: c1aabdf379bc ("can-gw: add netlink based CAN routing")
Cc: linux-stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -596,6 +596,7 @@ 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);
 			}
 		}
@@ -1154,6 +1155,7 @@ 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);
 	}
 }
@@ -1222,6 +1224,7 @@ 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;