macvlan: fix passthru mode race between dev removal and rx path
Currently, if macvlan in passthru mode is created and data are rxed and
you remove this device, following panic happens:
NULL pointer dereference at 0000000000000198
IP: [<ffffffffa0196058>] macvlan_handle_frame+0x153/0x1f7 [macvlan]
I'm using following script to trigger this:
<script>
while [ 1 ]
do
ip link add link e1 name macvtap0 type macvtap mode passthru
ip link set e1 up
ip link set macvtap0 up
IFINDEX=`ip link |grep macvtap0 | cut -f 1 -d ':'`
cat /dev/tap$IFINDEX >/dev/null &
ip link del dev macvtap0
done
</script>
I run this script while "ping -f" is running on another machine to send
packets to e1 rx.
Reason of the panic is that list_first_entry() is blindly called in
macvlan_handle_frame() even if the list was empty. vlan is set to
incorrect pointer which leads to the crash.
I'm fixing this by protecting port->vlans list by rcu and by preventing
from getting incorrect pointer in case the list is empty.
Introduced by: commit eb06acdc85585f2 "macvlan: Introduce 'passthru' mode to takeover the underlying device"
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index d5a141c..1c502bb 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -229,7 +229,8 @@
}
if (port->passthru)
- vlan = list_first_entry(&port->vlans, struct macvlan_dev, list);
+ vlan = list_first_or_null_rcu(&port->vlans,
+ struct macvlan_dev, list);
else
vlan = macvlan_hash_lookup(port, eth->h_dest);
if (vlan == NULL)
@@ -814,7 +815,7 @@
if (err < 0)
goto upper_dev_unlink;
- list_add_tail(&vlan->list, &port->vlans);
+ list_add_tail_rcu(&vlan->list, &port->vlans);
netif_stacked_transfer_operstate(lowerdev, dev);
return 0;
@@ -842,7 +843,7 @@
{
struct macvlan_dev *vlan = netdev_priv(dev);
- list_del(&vlan->list);
+ list_del_rcu(&vlan->list);
unregister_netdevice_queue(dev, head);
netdev_upper_dev_unlink(vlan->lowerdev, dev);
}