Re: [PATCH] net: bridge: add missing NULL checks

[Nikolay Aleksandrov]

On 08/04/18 20:49, Laszlo Toth wrote:

br_port_get_rtnl() can return NULL

Signed-off-by: Laszlo Toth <lasz...@gmail.com>
---
  net/bridge/br_netlink.c | 12 ++++++++++--
  1 file changed, 10 insertions(+), 2 deletions(-)

Nacked-by: Nikolay Aleksandrov <niko...@cumulusnetworks.com>
More below.

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 015f465c..cbec11f 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -939,14 +939,17 @@ static int br_port_slave_changelink(struct net_device 
*brdev,
                                    struct nlattr *data[],
                                    struct netlink_ext_ack *extack)
  {
+       struct net_bridge_port *port = br_port_get_rtnl(dev);
        struct net_bridge *br = netdev_priv(brdev);
        int ret;

if (!data)

                return 0;
+       if (!port)
+               return -EINVAL;

If we're here, it means the master device of dev is a bridge => dev is a bridge 
port,
since we're running with RTNL that cannot change, so this check is unnecessary.

Have you actually hit a bug with this code ?

        spin_lock_bh(&br->lock);
-       ret = br_setport(br_port_get_rtnl(dev), data);
+       ret = br_setport(port, data);
        spin_unlock_bh(&br->lock);

return ret;

@@ -956,7 +959,12 @@ static int br_port_fill_slave_info(struct sk_buff *skb,
                                   const struct net_device *brdev,
                                   const struct net_device *dev)
  {
-       return br_port_fill_attrs(skb, br_port_get_rtnl(dev));
+       struct net_bridge_port *port = br_port_get_rtnl(dev);
+
+       if (!port)
+               return -EINVAL;
+
+       return br_port_fill_attrs(skb, port);

Same rationale here, fill_slave_info is called via a master device's ops
under RTNL, which means dev is a bridge port and that also cannot change.

If you have hit a bug with this code, can we see the trace ?
The problem might be elsewhere.

Thanks,
 Nik

  }

static size_t br_port_get_slave_size(const struct net_device *brdev,