net: fix dev_seq_next()
Commit c6d14c84566d (net: Introduce for_each_netdev_rcu() iterator)
added a race in dev_seq_next().
The rcu_dereference() call should be done _before_ testing the end of
list, or we might return a wrong net_device if a concurrent thread
changes net_device list under us.
Note : discovered thanks to a sparse warning :
net/core/dev.c:3919:9: error: incompatible types in comparison expression
(different address spaces)
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 1b4c07f..ddd5df2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4051,12 +4051,15 @@
void *dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
- struct net_device *dev = (v == SEQ_START_TOKEN) ?
- first_net_device(seq_file_net(seq)) :
- next_net_device((struct net_device *)v);
+ struct net_device *dev = v;
+
+ if (v == SEQ_START_TOKEN)
+ dev = first_net_device_rcu(seq_file_net(seq));
+ else
+ dev = next_net_device_rcu(dev);
++*pos;
- return rcu_dereference(dev);
+ return dev;
}
void dev_seq_stop(struct seq_file *seq, void *v)