br2684: don't send frames on not-ready vcc

Avoid submitting packets to a vcc which is being closed. Things go badly
wrong when the ->pop method gets later called after everything's been
torn down.

Use the ATM socket lock for synchronisation with vcc_destroy_socket(),
which clears the ATM_VF_READY bit under the same lock. Otherwise, we
could end up submitting a packet to the device driver even after its
->ops->close method has been called. And it could call the vcc's ->pop
method after the protocol has been shut down. Which leads to a panic.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Acked-by: Krzysztof Mazur <krzysiek@podlesie.net>

1 files changed, 40 insertions, 3 deletions

diff --git a/net/atm/br2684.c b/net/atm/br2684.c
index 8eb6fbe8d8dd..4de3ae7bc3e2 100644
--- a/net/atm/br2684.c
+++ b/net/atm/br2684.c
@@ -68,6 +68,7 @@ struct br2684_vcc {
         /* keep old push, pop functions for chaining */
         void (*old_push)(struct atm_vcc *vcc, struct sk_buff *skb);
         void (*old_pop)(struct atm_vcc *vcc, struct sk_buff *skb);
+        void (*old_release_cb)(struct atm_vcc *vcc);
         enum br2684_encaps encaps;
         struct list_head brvccs;
 #ifdef CONFIG_ATM_BR2684_IPFILTER
@@ -269,6 +270,17 @@ static int br2684_xmit_vcc(struct sk_buff *skb, struct net_device *dev,
         return !atmvcc->send(atmvcc, skb);
 }
 
+static void br2684_release_cb(struct atm_vcc *atmvcc)
+{
+        struct br2684_vcc *brvcc = BR2684_VCC(atmvcc);
+
+        if (atomic_read(&brvcc->qspace) > 0)
+                netif_wake_queue(brvcc->device);
+
+        if (brvcc->old_release_cb)
+                brvcc->old_release_cb(atmvcc);
+}
+
 static inline struct br2684_vcc *pick_outgoing_vcc(const struct sk_buff *skb,
                                                    const struct br2684_dev *brdev)
 {
@@ -280,6 +292,8 @@ static netdev_tx_t br2684_start_xmit(struct sk_buff *skb,
 {
         struct br2684_dev *brdev = BRPRIV(dev);
         struct br2684_vcc *brvcc;
+        struct atm_vcc *atmvcc;
+        netdev_tx_t ret = NETDEV_TX_OK;
 
         pr_debug("skb_dst(skb)=%p\n", skb_dst(skb));
         read_lock(&devs_lock);
@@ -290,9 +304,26 @@ static netdev_tx_t br2684_start_xmit(struct sk_buff *skb,
                 dev->stats.tx_carrier_errors++;
                 /* netif_stop_queue(dev); */
                 dev_kfree_skb(skb);
-                read_unlock(&devs_lock);
-                return NETDEV_TX_OK;
+                goto out_devs;
         }
+        atmvcc = brvcc->atmvcc;
+
+        bh_lock_sock(sk_atm(atmvcc));
+
+        if (test_bit(ATM_VF_RELEASED, &atmvcc->flags) ||
+            test_bit(ATM_VF_CLOSE, &atmvcc->flags) ||
+            !test_bit(ATM_VF_READY, &atmvcc->flags)) {
+                dev->stats.tx_dropped++;
+                dev_kfree_skb(skb);
+                goto out;
+        }
+
+        if (sock_owned_by_user(sk_atm(atmvcc))) {
+                netif_stop_queue(brvcc->device);
+                ret = NETDEV_TX_BUSY;
+                goto out;
+        }
+
         if (!br2684_xmit_vcc(skb, dev, brvcc)) {
                 /*
                  * We should probably use netif_*_queue() here, but that
@@ -304,8 +335,11 @@ static netdev_tx_t br2684_start_xmit(struct sk_buff *skb,
                 dev->stats.tx_errors++;
                 dev->stats.tx_fifo_errors++;
         }
+ out:
+        bh_unlock_sock(sk_atm(atmvcc));
+ out_devs:
         read_unlock(&devs_lock);
-        return NETDEV_TX_OK;
+        return ret;
 }
 
 /*
@@ -378,6 +412,7 @@ static void br2684_close_vcc(struct br2684_vcc *brvcc)
         list_del(&brvcc->brvccs);
         write_unlock_irq(&devs_lock);
         brvcc->atmvcc->user_back = NULL;        /* what about vcc->recvq ??? */
+        brvcc->atmvcc->release_cb = brvcc->old_release_cb;
         brvcc->old_push(brvcc->atmvcc, NULL);   /* pass on the bad news */
         kfree(brvcc);
         module_put(THIS_MODULE);
@@ -554,9 +589,11 @@ static int br2684_regvcc(struct atm_vcc *atmvcc, void __user * arg)
         brvcc->encaps = (enum br2684_encaps)be.encaps;
         brvcc->old_push = atmvcc->push;
         brvcc->old_pop = atmvcc->pop;
+        brvcc->old_release_cb = atmvcc->release_cb;
         barrier();
         atmvcc->push = br2684_push;
         atmvcc->pop = br2684_pop;
+        atmvcc->release_cb = br2684_release_cb;
 
         /* initialize netdev carrier state */
         if (atmvcc->dev->signal == ATM_PHY_SIG_LOST)