PATCH? net/bridge/br_if.c: fix use after free in port_carrier_check()

Oleg Nesterov
2007-02-19T22:11:33Z

On 02/19, Oleg Nesterov wrote:
>
> I think the fix should be so that port_carrier_check() does get/put on
> "struct net_bridge_port" (container), but not on "struct net_device", and
>
> del_nbp(struct net_bridge_port *p)
>
> if (cancel_delayed_work(&p->carrier_check))
> - dev_put(p->dev);
> + kobject_put(&p->kobj);

Perhaps something like the patch below? (on top of this patch).
We should do something, the stable tree has the same bug.

Oleg.

--- WQ/net/bridge/br_if.c~5_bridge_uaf 2007-02-18 23:06:15.000000000 +0300
+++ WQ/net/bridge/br_if.c 2007-02-20 00:59:54.000000000 +0300
@@ -83,14 +83,14 @@ static void port_carrier_check(struct wo
struct net_device *dev;
struct net_bridge *br;

- dev = container_of(work, struct net_bridge_port,
- carrier_check.work)->dev;
+ p = container_of(work, struct net_bridge_port, carrier_check.work);

rtnl_lock();
- p = dev->br_port;
- if (!p)
- goto done;
br = p->br;
+ dev = p->dev;
+
+ if (!dev->br_port)
+ goto done;

if (netif_carrier_ok(dev))
p->path_cost = port_cost(dev);
@@ -107,14 +107,16 @@ static void port_carrier_check(struct wo
spin_unlock_bh(&br->lock);
}
done:
- dev_put(dev);
rtnl_unlock();
+ kobject_put(&p->kobj);
}

static void release_nbp(struct kobject *kobj)
{
struct net_bridge_port *p
= container_of(kobj, struct net_bridge_port, kobj);
+
+ dev_put(p->dev);
kfree(p);
}

@@ -127,12 +129,6 @@ static struct kobj_type brport_ktype = {

static void destroy_nbp(struct net_bridge_port *p)
{
- struct net_device *dev = p->dev;
-
- p->br = NULL;
- p->dev = NULL;
- dev_put(dev);
-
kobject_put(&p->kobj);
}

@@ -162,7 +158,7 @@ static void del_nbp(struct net_bridge_po
dev_set_promiscuity(dev, -1);

if (cancel_delayed_work(&p->carrier_check))
- dev_put(dev);
+ kobject_put(&p->kobj);

spin_lock_bh(&br->lock);
br_stp_disable_port(p);
@@ -446,7 +442,7 @@ int br_add_if(struct net_bridge *br, str
br_stp_recalculate_bridge_id(br);
br_features_recompute(br);
if (schedule_delayed_work(&p->carrier_check, BR_PORT_DEBOUNCE))
- dev_hold(dev);
+ kobject_get(&p->kobj);

spin_unlock_bh(&br->lock);