atm: fix a UAF in lec_arp_clear_vccs()

Gengming reported a UAF in lec_arp_clear_vccs(),
where we add a vcc socket to an entry in a per-device
list but free the socket without removing it from the
list when vcc->dev is NULL.

We need to call lec_vcc_close() to search and remove
those entries contain the vcc being destroyed. This can
be done by calling vcc->push(vcc, NULL) unconditionally
in vcc_destroy_socket().

Another issue discovered by Gengming's reproducer is
the vcc->dev may point to the static device lecatm_dev,
for which we don't need to register/unregister device,
so we can just check for vcc->dev->ops->owner.

Reported-by: Gengming Liu <l.dmxcsnsbh@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/atm/common.c b/net/atm/common.c
index 0ce530a..8575f5d 100644 (file)
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -177,18 +177,18 @@ static void vcc_destroy_socket(struct sock *sk)
 
        set_bit(ATM_VF_CLOSE, &vcc->flags);
        clear_bit(ATM_VF_READY, &vcc->flags);
-       if (vcc->dev) {
-               if (vcc->dev->ops->close)
-                       vcc->dev->ops->close(vcc);
-               if (vcc->push)
-                       vcc->push(vcc, NULL); /* atmarpd has no push */
-               module_put(vcc->owner);
-
-               while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
-                       atm_return(vcc, skb->truesize);
-                       kfree_skb(skb);
-               }
+       if (vcc->dev && vcc->dev->ops->close)
+               vcc->dev->ops->close(vcc);
+       if (vcc->push)
+               vcc->push(vcc, NULL); /* atmarpd has no push */
+       module_put(vcc->owner);
+
+       while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+               atm_return(vcc, skb->truesize);
+               kfree_skb(skb);
+       }
 
+       if (vcc->dev && vcc->dev->ops->owner) {
                module_put(vcc->dev->ops->owner);
                atm_dev_put(vcc->dev);
        }