[ 3.5.y.z extended stable ] Patch "macvlan: fix passthru mode race between dev removal and rx" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    macvlan: fix passthru mode race between dev removal and rx

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 64fb023ce61a991ff49dcc29da0751acc193567a Mon Sep 17 00:00:00 2001
From: Jiri Pirko <jiri at resnulli.us>
Date: Thu, 9 May 2013 04:23:40 +0000
Subject: [PATCH] macvlan: fix passthru mode race between dev removal and rx
 path

commit 233c7df0821c4190e2d3f4be0f2ca0ab40a5ed8c upstream.

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 at resnulli.us>
Acked-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/macvlan.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 666fc20..0bec603 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -204,7 +204,8 @@ static rx_handler_result_t macvlan_handle_frame(struct sk_buff **pskb)
 	}

 	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)
@@ -771,7 +772,7 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev,
 	if (err < 0)
 		goto destroy_port;

-	list_add_tail(&vlan->list, &port->vlans);
+	list_add_tail_rcu(&vlan->list, &port->vlans);
 	netif_stacked_transfer_operstate(lowerdev, dev);

 	return 0;
@@ -797,7 +798,7 @@ void macvlan_dellink(struct net_device *dev, struct list_head *head)
 {
 	struct macvlan_dev *vlan = netdev_priv(dev);

-	list_del(&vlan->list);
+	list_del_rcu(&vlan->list);
 	unregister_netdevice_queue(dev, head);
 }
 EXPORT_SYMBOL_GPL(macvlan_dellink);
--
1.8.1.2