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

Commit b19cbe2a authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
Browse files

[BRIDGE]: Fix fdb RCU race 



br_fdb_get use atomic_inc to increase the refcount of an element found
on a RCU protected list, which can lead to the following race:

CPU0					CPU1

					br_fdb_get:   rcu_read_lock
					__br_fdb_get: find element
fdb_delete:   hlist_del_rcu
	      br_fdb_put
br_fdb_put:   atomic_dec_and_test
	      call_rcu(fdb_rcu_free)	br_fdb_get:   atomic_inc
						      rcu_read_unlock
fdb_rcu_free: kmem_cache_free

Use atomic_inc_not_zero instead.

Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ec25615b

net/bridge/br_fdb.c

+2 −2
Original line number Diff line number Diff line
@@ -197,8 +197,8 @@ struct net_bridge_fdb_entry *br_fdb_get(struct net_bridge *br, 


	rcu_read_lock();

	fdb = __br_fdb_get(br, addr);

	if (fdb)

		atomic_inc(&fdb->use_count);

	if (fdb && !atomic_inc_not_zero(&fdb->use_count))

		fdb = NULL;

	rcu_read_unlock();

	return fdb;

}