On Mon, Apr 09, 2018 at 01:25:41AM +0300, Nikolay Aleksandrov wrote:
> 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.
There was a NULL dereference in br_port_fill_attrs(), but on a much
older release w/ a probably buggy and custom driver,
so there is no real problem to trace.
Anyway I thought I'd make a quick patch from it, but you're right,
it's pointless to validate twice.
Please just ignore the patch.
Laszlo
>
> Thanks,
> Nik
>
> > }
> > static size_t br_port_get_slave_size(const struct net_device *brdev,
> >
>
