usbnet: fix skb traversing races during unlink(v2)
Ming Lei [Thu, 26 Apr 2012 03:33:46 +0000 (11:33 +0800)]
Commit 4231d47e6fe69f061f96c98c30eaf9fb4c14b96d(net/usbnet: avoid
recursive locking in usbnet_stop()) fixes the recursive locking
problem by releasing the skb queue lock before unlink, but may
cause skb traversing races:
- after URB is unlinked and the queue lock is released,
the refered skb and skb->next may be moved to done queue,
even be released
- in skb_queue_walk_safe, the next skb is still obtained
by next pointer of the last skb
- so maybe trigger oops or other problems

This patch extends the usage of entry->state to describe 'start_unlink'
state, so always holding the queue(rx/tx) lock to change the state if
the referd skb is in rx or tx queue because we need to know if the
refered urb has been started unlinking in unlink_urbs.

The other part of this patch is based on Huajun's patch:
always traverse from head of the tx/rx queue to get skb which is
to be unlinked but not been started unlinking.

Signed-off-by: Huajun Li <huajun.li.lee@gmail.com>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Cc: Oliver Neukum <oneukum@suse.de>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/usbnet.c
include/linux/usb/usbnet.h

index 2d927fb..b38db48 100644 (file)
@@ -282,17 +282,32 @@ int usbnet_change_mtu (struct net_device *net, int new_mtu)
 }
 EXPORT_SYMBOL_GPL(usbnet_change_mtu);
 
+/* The caller must hold list->lock */
+static void __usbnet_queue_skb(struct sk_buff_head *list,
+                       struct sk_buff *newsk, enum skb_state state)
+{
+       struct skb_data *entry = (struct skb_data *) newsk->cb;
+
+       __skb_queue_tail(list, newsk);
+       entry->state = state;
+}
+
 /*-------------------------------------------------------------------------*/
 
 /* some LK 2.4 HCDs oopsed if we freed or resubmitted urbs from
  * completion callbacks.  2.5 should have fixed those bugs...
  */
 
-static void defer_bh(struct usbnet *dev, struct sk_buff *skb, struct sk_buff_head *list)
+static enum skb_state defer_bh(struct usbnet *dev, struct sk_buff *skb,
+               struct sk_buff_head *list, enum skb_state state)
 {
        unsigned long           flags;
+       enum skb_state          old_state;
+       struct skb_data *entry = (struct skb_data *) skb->cb;
 
        spin_lock_irqsave(&list->lock, flags);
+       old_state = entry->state;
+       entry->state = state;
        __skb_unlink(skb, list);
        spin_unlock(&list->lock);
        spin_lock(&dev->done.lock);
@@ -300,6 +315,7 @@ static void defer_bh(struct usbnet *dev, struct sk_buff *skb, struct sk_buff_hea
        if (dev->done.qlen == 1)
                tasklet_schedule(&dev->bh);
        spin_unlock_irqrestore(&dev->done.lock, flags);
+       return old_state;
 }
 
 /* some work can't be done in tasklets, so we use keventd
@@ -340,7 +356,6 @@ static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
        entry = (struct skb_data *) skb->cb;
        entry->urb = urb;
        entry->dev = dev;
-       entry->state = rx_start;
        entry->length = 0;
 
        usb_fill_bulk_urb (urb, dev->udev, dev->in,
@@ -372,7 +387,7 @@ static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
                        tasklet_schedule (&dev->bh);
                        break;
                case 0:
-                       __skb_queue_tail (&dev->rxq, skb);
+                       __usbnet_queue_skb(&dev->rxq, skb, rx_start);
                }
        } else {
                netif_dbg(dev, ifdown, dev->net, "rx: stopped\n");
@@ -423,16 +438,17 @@ static void rx_complete (struct urb *urb)
        struct skb_data         *entry = (struct skb_data *) skb->cb;
        struct usbnet           *dev = entry->dev;
        int                     urb_status = urb->status;
+       enum skb_state          state;
 
        skb_put (skb, urb->actual_length);
-       entry->state = rx_done;
+       state = rx_done;
        entry->urb = NULL;
 
        switch (urb_status) {
        /* success */
        case 0:
                if (skb->len < dev->net->hard_header_len) {
-                       entry->state = rx_cleanup;
+                       state = rx_cleanup;
                        dev->net->stats.rx_errors++;
                        dev->net->stats.rx_length_errors++;
                        netif_dbg(dev, rx_err, dev->net,
@@ -471,7 +487,7 @@ static void rx_complete (struct urb *urb)
                                  "rx throttle %d\n", urb_status);
                }
 block:
-               entry->state = rx_cleanup;
+               state = rx_cleanup;
                entry->urb = urb;
                urb = NULL;
                break;
@@ -482,17 +498,18 @@ block:
                // FALLTHROUGH
 
        default:
-               entry->state = rx_cleanup;
+               state = rx_cleanup;
                dev->net->stats.rx_errors++;
                netif_dbg(dev, rx_err, dev->net, "rx status %d\n", urb_status);
                break;
        }
 
-       defer_bh(dev, skb, &dev->rxq);
+       state = defer_bh(dev, skb, &dev->rxq, state);
 
        if (urb) {
                if (netif_running (dev->net) &&
-                   !test_bit (EVENT_RX_HALT, &dev->flags)) {
+                   !test_bit (EVENT_RX_HALT, &dev->flags) &&
+                   state != unlink_start) {
                        rx_submit (dev, urb, GFP_ATOMIC);
                        usb_mark_last_busy(dev->udev);
                        return;
@@ -579,16 +596,23 @@ EXPORT_SYMBOL_GPL(usbnet_purge_paused_rxq);
 static int unlink_urbs (struct usbnet *dev, struct sk_buff_head *q)
 {
        unsigned long           flags;
-       struct sk_buff          *skb, *skbnext;
+       struct sk_buff          *skb;
        int                     count = 0;
 
        spin_lock_irqsave (&q->lock, flags);
-       skb_queue_walk_safe(q, skb, skbnext) {
+       while (!skb_queue_empty(q)) {
                struct skb_data         *entry;
                struct urb              *urb;
                int                     retval;
 
-               entry = (struct skb_data *) skb->cb;
+               skb_queue_walk(q, skb) {
+                       entry = (struct skb_data *) skb->cb;
+                       if (entry->state != unlink_start)
+                               goto found;
+               }
+               break;
+found:
+               entry->state = unlink_start;
                urb = entry->urb;
 
                /*
@@ -1039,8 +1063,7 @@ static void tx_complete (struct urb *urb)
        }
 
        usb_autopm_put_interface_async(dev->intf);
-       entry->state = tx_done;
-       defer_bh(dev, skb, &dev->txq);
+       (void) defer_bh(dev, skb, &dev->txq, tx_done);
 }
 
 /*-------------------------------------------------------------------------*/
@@ -1096,7 +1119,6 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
        entry = (struct skb_data *) skb->cb;
        entry->urb = urb;
        entry->dev = dev;
-       entry->state = tx_start;
        entry->length = length;
 
        usb_fill_bulk_urb (urb, dev->udev, dev->out,
@@ -1155,7 +1177,7 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
                break;
        case 0:
                net->trans_start = jiffies;
-               __skb_queue_tail (&dev->txq, skb);
+               __usbnet_queue_skb(&dev->txq, skb, tx_start);
                if (dev->txq.qlen >= TX_QLEN (dev))
                        netif_stop_queue (net);
        }
index 605b0aa..76f4396 100644 (file)
@@ -191,7 +191,8 @@ extern void usbnet_cdc_status(struct usbnet *, struct urb *);
 enum skb_state {
        illegal = 0,
        tx_start, tx_done,
-       rx_start, rx_done, rx_cleanup
+       rx_start, rx_done, rx_cleanup,
+       unlink_start
 };
 
 struct skb_data {      /* skb->cb is one of these */