bridge: netlink: fix slave_changelink/br_setport race conditions

Since slave_changelink support was added there have been a few race
conditions when using br_setport() since some of the port functions it
uses require the bridge lock. It is very easy to trigger a lockup due to
some internal spin_lock() usage without bh disabled, also it's possible to
get the bridge into an inconsistent state.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Fixes: 3ac636b8591c ("bridge: implement rtnl_link_ops->slave_changelink")
Reviewed-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 1 deletions

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 364bdc98bd9b..3da5525eb8a2 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -693,9 +693,17 @@ static int br_port_slave_changelink(struct net_device *brdev,
                                     struct nlattr *tb[],
                                     struct nlattr *data[])
 {
+        struct net_bridge *br = netdev_priv(brdev);
+        int ret;
+
         if (!data)
                 return 0;
-        return br_setport(br_port_get_rtnl(dev), data);
+
+        spin_lock_bh(&br->lock);
+        ret = br_setport(br_port_get_rtnl(dev), data);
+        spin_unlock_bh(&br->lock);
+
+        return ret;
 }
 
 static int br_port_fill_slave_info(struct sk_buff *skb,