Patch "macvlan: fix passthru mode race between dev removal and rx path" has been added to the 3.4-stable tree

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This is a note to let you know that I've just added the patch titled

    macvlan: fix passthru mode race between dev removal and rx path

to the 3.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     macvlan-fix-passthru-mode-race-between-dev-removal-and-rx-path.patch
and it can be found in the queue-3.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From be2f1b1ca3363534ddc26b854290688471d7d973 Mon Sep 17 00:00:00 2001
From: Jiri Pirko <jiri@xxxxxxxxxxx>
Date: Thu, 9 May 2013 04:23:40 +0000
Subject: macvlan: fix passthru mode race between dev removal and rx path


From: Jiri Pirko <jiri@xxxxxxxxxxx>

[ Upstream commit 233c7df0821c4190e2d3f4be0f2ca0ab40a5ed8c, note
  that I had to add list_first_or_null_rcu to rculist.h in order
  to accomodate this fix. ]

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@xxxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/macvlan.c   |    7 ++++---
 include/linux/rculist.h |   17 +++++++++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -205,7 +205,8 @@ static rx_handler_result_t macvlan_handl
 	}
 
 	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)
@@ -724,7 +725,7 @@ int macvlan_common_newlink(struct net *s
 	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;
@@ -750,7 +751,7 @@ void macvlan_dellink(struct net_device *
 {
 	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);
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -242,6 +242,23 @@ static inline void list_splice_init_rcu(
 	list_entry_rcu((ptr)->next, type, member)
 
 /**
+ * list_first_or_null_rcu - get the first element from a list
+ * @ptr:        the list head to take the element from.
+ * @type:       the type of the struct this is embedded in.
+ * @member:     the name of the list_struct within the struct.
+ *
+ * Note that if the list is empty, it returns NULL.
+ *
+ * This primitive may safely run concurrently with the _rcu list-mutation
+ * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
+ */
+#define list_first_or_null_rcu(ptr, type, member) \
+	({struct list_head *__ptr = (ptr); \
+	  struct list_head __rcu *__next = list_next_rcu(__ptr); \
+	  likely(__ptr != __next) ? container_of(__next, type, member) : NULL; \
+	})
+
+/**
  * list_for_each_entry_rcu	-	iterate over rcu list of given type
  * @pos:	the type * to use as a loop cursor.
  * @head:	the head for your list.


Patches currently in stable-queue which might be from jiri@xxxxxxxxxxx are

queue-3.4/macvlan-fix-passthru-mode-race-between-dev-removal-and-rx-path.patch
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