wimax/i2400m: fix i2400m->wake_tx_skb handling

i2400m_net_wake_tx() sets ->wake_tx_skb with the given skb if
->wake_tx_ws is not pending; however, i2400m_wake_tx_work() could have
just started execution and haven't fetched -><wake_tx_skb yet.  The
previous packet will be leaked.

Update ->wake_tx_skb handling.

* i2400m_net_wake_tx() now tests whether the previous ->wake_tx_skb
  has been consumed by ->wake_tx_ws instead of testing work_pending().

* i2400m_net_wake_stop() is simplified similarly.  It always puts
  ->wake_tx_skb if non-NULL.

* Spurious ->wake_tx_skb dereference outside critical section dropped
  from i2400m_wake_tx_work().

Only compile tested.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Dan Williams <dcbw@redhat.com>
Cc: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
Cc: linux-wimax@intel.com
Cc: wimax@linuxwimax.org

1 files changed, 17 insertions, 14 deletions

diff --git a/drivers/net/wimax/i2400m/netdev.c b/drivers/net/wimax/i2400m/netdev.c
index 1d76ae855f07..530581ca0191 100644
--- a/drivers/net/wimax/i2400m/netdev.c
+++ b/drivers/net/wimax/i2400m/netdev.c
@@ -156,7 +156,7 @@ void i2400m_wake_tx_work(struct work_struct *ws)
         struct i2400m *i2400m = container_of(ws, struct i2400m, wake_tx_ws);
         struct net_device *net_dev = i2400m->wimax_dev.net_dev;
         struct device *dev = i2400m_dev(i2400m);
-        struct sk_buff *skb = i2400m->wake_tx_skb;
+        struct sk_buff *skb;
         unsigned long flags;
 
         spin_lock_irqsave(&i2400m->tx_lock, flags);
@@ -236,23 +236,26 @@ void i2400m_tx_prep_header(struct sk_buff *skb)
 void i2400m_net_wake_stop(struct i2400m *i2400m)
 {
         struct device *dev = i2400m_dev(i2400m);
+        struct sk_buff *wake_tx_skb;
+        unsigned long flags;
 
         d_fnstart(3, dev, "(i2400m %p)\n", i2400m);
-        /* See i2400m_hard_start_xmit(), references are taken there
-         * and here we release them if the work was still
-         * pending. Note we can't differentiate work not pending vs
-         * never scheduled, so the NULL check does that. */
-        if (cancel_work_sync(&i2400m->wake_tx_ws) == 0
-            && i2400m->wake_tx_skb != NULL) {
-                unsigned long flags;
-                struct sk_buff *wake_tx_skb;
-                spin_lock_irqsave(&i2400m->tx_lock, flags);
-                wake_tx_skb = i2400m->wake_tx_skb;      /* compat help */
-                i2400m->wake_tx_skb = NULL;     /* compat help */
-                spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+        /*
+         * See i2400m_hard_start_xmit(), references are taken there and
+         * here we release them if the packet was still pending.
+         */
+        cancel_work_sync(&i2400m->wake_tx_ws);
+
+        spin_lock_irqsave(&i2400m->tx_lock, flags);
+        wake_tx_skb = i2400m->wake_tx_skb;
+        i2400m->wake_tx_skb = NULL;
+        spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+
+        if (wake_tx_skb) {
                 i2400m_put(i2400m);
                 kfree_skb(wake_tx_skb);
         }
+
         d_fnend(3, dev, "(i2400m %p) = void\n", i2400m);
 }
 
@@ -288,7 +291,7 @@ int i2400m_net_wake_tx(struct i2400m *i2400m, struct net_device *net_dev,
          * and if pending, release those resources. */
         result = 0;
         spin_lock_irqsave(&i2400m->tx_lock, flags);
-        if (!work_pending(&i2400m->wake_tx_ws)) {
+        if (!i2400m->wake_tx_skb) {
                 netif_stop_queue(net_dev);
                 i2400m_get(i2400m);
                 i2400m->wake_tx_skb = skb_get(skb);     /* transfer ref count */