Commit b19cbe2a authored Mar 22, 2007 by Patrick McHardy Committed by David S. Miller Mar 22, 2007

[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: Patrick McHardy <kaber@trash.net>
Signed-off-by: David 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;
		}

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