[3.16.y-ckt stable] Patch "team: fix possible null pointer dereference in team_handle_frame" has been added to staging queue

[Luis Henriques]

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

    team: fix possible null pointer dereference in team_handle_frame

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt9.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From ff95c653c09182b0efa71a8c083b77c2b5f2db30 Mon Sep 17 00:00:00 2001
From: Jiri Pirko <jiri at resnulli.us>
Date: Mon, 23 Feb 2015 14:02:54 +0100
Subject: team: fix possible null pointer dereference in team_handle_frame

commit 57e595631904c827cfa1a0f7bbd7cc9a49da5745 upstream.

Currently following race is possible in team:

CPU0                                        CPU1
                                            team_port_del
                                              team_upper_dev_unlink
                                                priv_flags &= ~IFF_TEAM_PORT
team_handle_frame
  team_port_get_rcu
    team_port_exists
      priv_flags & IFF_TEAM_PORT == 0
    return NULL (instead of port got
                 from rx_handler_data)
                                              netdev_rx_handler_unregister

The thing is that the flag is removed before rx_handler is unregistered.
If team_handle_frame is called in between, team_port_exists returns 0
and team_port_get_rcu will return NULL.
So do not check the flag here. It is guaranteed by netdev_rx_handler_unregister
that team_handle_frame will always see valid rx_handler_data pointer.

Signed-off-by: Jiri Pirko <jiri at resnulli.us>
Fixes: 3d249d4ca7d0 ("net: introduce ethernet teaming device")
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/team/team.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
index 3dd334a29fcf..fa977f9c2e5f 100644
--- a/drivers/net/team/team.c
+++ b/drivers/net/team/team.c
@@ -42,9 +42,7 @@

 static struct team_port *team_port_get_rcu(const struct net_device *dev)
 {
-	struct team_port *port = rcu_dereference(dev->rx_handler_data);
-
-	return team_port_exists(dev) ? port : NULL;
+	return rcu_dereference(dev->rx_handler_data);
 }

 static struct team_port *team_port_get_rtnl(const struct net_device *dev)