usb gadget: g_ether spinlock recursion fix

The new spinlock debug code turned up a spinlock recursion bug in the
Ethernet gadget driver on a disconnect path; it would show up with any
UDC driver where the cancellation of active requests was synchronous,
rather than e.g. delayed until a controller's completion IRQ.

That recursion is fixed here by creating and using a new spinlock to
protect the relevant lists.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 31 insertions, 14 deletions

diff --git a/drivers/usb/gadget/ether.c b/drivers/usb/gadget/ether.c
index 4fe1bec1c255..30299c620d97 100644
--- a/drivers/usb/gadget/ether.c
+++ b/drivers/usb/gadget/ether.c
@@ -117,6 +117,8 @@ struct eth_dev {
         struct usb_ep           *in_ep, *out_ep, *status_ep;
         const struct usb_endpoint_descriptor
                                 *in, *out, *status;
+
+        spinlock_t              req_lock;
         struct list_head        tx_reqs, rx_reqs;
 
         struct net_device       *net;
@@ -1066,21 +1068,31 @@ static void eth_reset_config (struct eth_dev *dev)
          */
         if (dev->in) {
                 usb_ep_disable (dev->in_ep);
+                spin_lock(&dev->req_lock);
                 while (likely (!list_empty (&dev->tx_reqs))) {
                         req = container_of (dev->tx_reqs.next,
                                                 struct usb_request, list);
                         list_del (&req->list);
+
+                        spin_unlock(&dev->req_lock);
                         usb_ep_free_request (dev->in_ep, req);
+                        spin_lock(&dev->req_lock);
                 }
+                spin_unlock(&dev->req_lock);
         }
         if (dev->out) {
                 usb_ep_disable (dev->out_ep);
+                spin_lock(&dev->req_lock);
                 while (likely (!list_empty (&dev->rx_reqs))) {
                         req = container_of (dev->rx_reqs.next,
                                                 struct usb_request, list);
                         list_del (&req->list);
+
+                        spin_unlock(&dev->req_lock);
                         usb_ep_free_request (dev->out_ep, req);
+                        spin_lock(&dev->req_lock);
                 }
+                spin_unlock(&dev->req_lock);
         }
 
         if (dev->status) {
@@ -1659,9 +1671,9 @@ enomem:
         if (retval) {
                 DEBUG (dev, "rx submit --> %d\n", retval);
                 dev_kfree_skb_any (skb);
-                spin_lock (&dev->lock);
+                spin_lock(&dev->req_lock);
                 list_add (&req->list, &dev->rx_reqs);
-                spin_unlock (&dev->lock);
+                spin_unlock(&dev->req_lock);
         }
         return retval;
 }
@@ -1730,8 +1742,9 @@ quiesce:
                 dev_kfree_skb_any (skb);
         if (!netif_running (dev->net)) {
 clean:
-                /* nobody reading rx_reqs, so no dev->lock */
+                spin_lock(&dev->req_lock);
                 list_add (&req->list, &dev->rx_reqs);
+                spin_unlock(&dev->req_lock);
                 req = NULL;
         }
         if (req)
@@ -1782,15 +1795,18 @@ static int alloc_requests (struct eth_dev *dev, unsigned n, gfp_t gfp_flags)
 {
         int status;
 
+        spin_lock(&dev->req_lock);
         status = prealloc (&dev->tx_reqs, dev->in_ep, n, gfp_flags);
         if (status < 0)
                 goto fail;
         status = prealloc (&dev->rx_reqs, dev->out_ep, n, gfp_flags);
         if (status < 0)
                 goto fail;
-        return 0;
+        goto done;
 fail:
         DEBUG (dev, "can't alloc requests\n");
+done:
+        spin_unlock(&dev->req_lock);
         return status;
 }
 
@@ -1800,21 +1816,21 @@ static void rx_fill (struct eth_dev *dev, gfp_t gfp_flags)
         unsigned long           flags;
 
         /* fill unused rxq slots with some skb */
-        spin_lock_irqsave (&dev->lock, flags);
+        spin_lock_irqsave(&dev->req_lock, flags);
         while (!list_empty (&dev->rx_reqs)) {
                 req = container_of (dev->rx_reqs.next,
                                 struct usb_request, list);
                 list_del_init (&req->list);
-                spin_unlock_irqrestore (&dev->lock, flags);
+                spin_unlock_irqrestore(&dev->req_lock, flags);
 
                 if (rx_submit (dev, req, gfp_flags) < 0) {
                         defer_kevent (dev, WORK_RX_MEMORY);
                         return;
                 }
 
-                spin_lock_irqsave (&dev->lock, flags);
+                spin_lock_irqsave(&dev->req_lock, flags);
         }
-        spin_unlock_irqrestore (&dev->lock, flags);
+        spin_unlock_irqrestore(&dev->req_lock, flags);
 }
 
 static void eth_work (void *_dev)
@@ -1848,9 +1864,9 @@ static void tx_complete (struct usb_ep *ep, struct usb_request *req)
         }
         dev->stats.tx_packets++;
 
-        spin_lock (&dev->lock);
+        spin_lock(&dev->req_lock);
         list_add (&req->list, &dev->tx_reqs);
-        spin_unlock (&dev->lock);
+        spin_unlock(&dev->req_lock);
         dev_kfree_skb_any (skb);
 
         atomic_dec (&dev->tx_qlen);
@@ -1896,12 +1912,12 @@ static int eth_start_xmit (struct sk_buff *skb, struct net_device *net)
                 /* ignores USB_CDC_PACKET_TYPE_DIRECTED */
         }
 
-        spin_lock_irqsave (&dev->lock, flags);
+        spin_lock_irqsave(&dev->req_lock, flags);
         req = container_of (dev->tx_reqs.next, struct usb_request, list);
         list_del (&req->list);
         if (list_empty (&dev->tx_reqs))
                 netif_stop_queue (net);
-        spin_unlock_irqrestore (&dev->lock, flags);
+        spin_unlock_irqrestore(&dev->req_lock, flags);
 
         /* no buffer copies needed, unless the network stack did it
          * or the hardware can't use skb buffers.
@@ -1955,11 +1971,11 @@ static int eth_start_xmit (struct sk_buff *skb, struct net_device *net)
 drop:
                 dev->stats.tx_dropped++;
                 dev_kfree_skb_any (skb);
-                spin_lock_irqsave (&dev->lock, flags);
+                spin_lock_irqsave(&dev->req_lock, flags);
                 if (list_empty (&dev->tx_reqs))
                         netif_start_queue (net);
                 list_add (&req->list, &dev->tx_reqs);
-                spin_unlock_irqrestore (&dev->lock, flags);
+                spin_unlock_irqrestore(&dev->req_lock, flags);
         }
         return 0;
 }
@@ -2378,6 +2394,7 @@ autoconf_fail:
                 return status;
         dev = netdev_priv(net);
         spin_lock_init (&dev->lock);
+        spin_lock_init (&dev->req_lock);
         INIT_WORK (&dev->work, eth_work, dev);
         INIT_LIST_HEAD (&dev->tx_reqs);
         INIT_LIST_HEAD (&dev->rx_reqs);