rtl8187: Use usb anchor facilities to manage urbs

When SLUB debugging is enabled in the kernel, and the boot command includes
the option "slub_debug=P", rtl8187 encounters a GPF due to a read-after-free
of a urb.

Following the example of changes in p54usb to fix the same problem, the code
has been modified to use the usb_anchor_urb() method. With this change, the
USB core handles the freeing of urb's.

This patch fixes the problem reported in Kernel Bugzilla #12185
(http://bugzilla.kernel.org/show_bug.cgi?id=12185).

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 52 insertions, 25 deletions

diff --git a/drivers/net/wireless/rtl818x/rtl8187.h b/drivers/net/wireless/rtl818x/rtl8187.h
index c385407a9941..3b1e1c2aad26 100644
--- a/drivers/net/wireless/rtl818x/rtl8187.h
+++ b/drivers/net/wireless/rtl818x/rtl8187.h
@@ -99,6 +99,7 @@ struct rtl8187_priv {
         struct ieee80211_supported_band band;
         struct usb_device *udev;
         u32 rx_conf;
+        struct usb_anchor anchored;
         u16 txpwr_base;
         u8 asic_rev;
         u8 is_rtl8187b;
@@ -115,7 +116,6 @@ struct rtl8187_priv {
         u8 aifsn[4];
         struct {
                 __le64 buf;
-                struct urb *urb;
                 struct sk_buff_head queue;
         } b_tx_status;
 };
diff --git a/drivers/net/wireless/rtl818x/rtl8187_dev.c b/drivers/net/wireless/rtl818x/rtl8187_dev.c
index 417a2d7b5764..74f5449b7924 100644
--- a/drivers/net/wireless/rtl818x/rtl8187_dev.c
+++ b/drivers/net/wireless/rtl818x/rtl8187_dev.c
@@ -99,7 +99,6 @@ static const struct ieee80211_channel rtl818x_channels[] = {
 static void rtl8187_iowrite_async_cb(struct urb *urb)
 {
         kfree(urb->context);
-        usb_free_urb(urb);
 }
 
 static void rtl8187_iowrite_async(struct rtl8187_priv *priv, __le16 addr,
@@ -136,11 +135,13 @@ static void rtl8187_iowrite_async(struct rtl8187_priv *priv, __le16 addr,
         usb_fill_control_urb(urb, priv->udev, usb_sndctrlpipe(priv->udev, 0),
                              (unsigned char *)dr, buf, len,
                              rtl8187_iowrite_async_cb, buf);
+        usb_anchor_urb(urb, &priv->anchored);
         rc = usb_submit_urb(urb, GFP_ATOMIC);
         if (rc < 0) {
                 kfree(buf);
-                usb_free_urb(urb);
+                usb_unanchor_urb(urb);
         }
+        usb_free_urb(urb);
 }
 
 static inline void rtl818x_iowrite32_async(struct rtl8187_priv *priv,
@@ -172,7 +173,6 @@ static void rtl8187_tx_cb(struct urb *urb)
         struct ieee80211_hw *hw = info->rate_driver_data[0];
         struct rtl8187_priv *priv = hw->priv;
 
-        usb_free_urb(info->rate_driver_data[1]);
         skb_pull(skb, priv->is_rtl8187b ? sizeof(struct rtl8187b_tx_hdr) :
                                           sizeof(struct rtl8187_tx_hdr));
         ieee80211_tx_info_clear_status(info);
@@ -273,11 +273,13 @@ static int rtl8187_tx(struct ieee80211_hw *dev, struct sk_buff *skb)
 
         usb_fill_bulk_urb(urb, priv->udev, usb_sndbulkpipe(priv->udev, ep),
                           buf, skb->len, rtl8187_tx_cb, skb);
+        usb_anchor_urb(urb, &priv->anchored);
         rc = usb_submit_urb(urb, GFP_ATOMIC);
         if (rc < 0) {
-                usb_free_urb(urb);
+                usb_unanchor_urb(urb);
                 kfree_skb(skb);
         }
+        usb_free_urb(urb);
 
         return 0;
 }
@@ -301,14 +303,13 @@ static void rtl8187_rx_cb(struct urb *urb)
                 return;
         }
         spin_unlock(&priv->rx_queue.lock);
+        skb_put(skb, urb->actual_length);
 
         if (unlikely(urb->status)) {
-                usb_free_urb(urb);
                 dev_kfree_skb_irq(skb);
                 return;
         }
 
-        skb_put(skb, urb->actual_length);
         if (!priv->is_rtl8187b) {
                 struct rtl8187_rx_hdr *hdr =
                         (typeof(hdr))(skb_tail_pointer(skb) - sizeof(*hdr));
@@ -361,7 +362,6 @@ static void rtl8187_rx_cb(struct urb *urb)
 
         skb = dev_alloc_skb(RTL8187_MAX_RX);
         if (unlikely(!skb)) {
-                usb_free_urb(urb);
                 /* TODO check rx queue length and refill *somewhere* */
                 return;
         }
@@ -373,24 +373,32 @@ static void rtl8187_rx_cb(struct urb *urb)
         urb->context = skb;
         skb_queue_tail(&priv->rx_queue, skb);
 
-        usb_submit_urb(urb, GFP_ATOMIC);
+        usb_anchor_urb(urb, &priv->anchored);
+        if (usb_submit_urb(urb, GFP_ATOMIC)) {
+                usb_unanchor_urb(urb);
+                skb_unlink(skb, &priv->rx_queue);
+                dev_kfree_skb_irq(skb);
+        }
 }
 
 static int rtl8187_init_urbs(struct ieee80211_hw *dev)
 {
         struct rtl8187_priv *priv = dev->priv;
-        struct urb *entry;
+        struct urb *entry = NULL;
         struct sk_buff *skb;
         struct rtl8187_rx_info *info;
+        int ret = 0;
 
         while (skb_queue_len(&priv->rx_queue) < 8) {
                 skb = __dev_alloc_skb(RTL8187_MAX_RX, GFP_KERNEL);
-                if (!skb)
-                        break;
+                if (!skb) {
+                        ret = -ENOMEM;
+                        goto err;
+                }
                 entry = usb_alloc_urb(0, GFP_KERNEL);
                 if (!entry) {
-                        kfree_skb(skb);
-                        break;
+                        ret = -ENOMEM;
+                        goto err;
                 }
                 usb_fill_bulk_urb(entry, priv->udev,
                                   usb_rcvbulkpipe(priv->udev,
@@ -401,10 +409,22 @@ static int rtl8187_init_urbs(struct ieee80211_hw *dev)
                 info->urb = entry;
                 info->dev = dev;
                 skb_queue_tail(&priv->rx_queue, skb);
-                usb_submit_urb(entry, GFP_KERNEL);
+                usb_anchor_urb(entry, &priv->anchored);
+                ret = usb_submit_urb(entry, GFP_KERNEL);
+                if (ret) {
+                        skb_unlink(skb, &priv->rx_queue);
+                        usb_unanchor_urb(entry);
+                        goto err;
+                }
+                usb_free_urb(entry);
         }
+        return ret;
 
-        return 0;
+err:
+        usb_free_urb(entry);
+        kfree_skb(skb);
+        usb_kill_anchored_urbs(&priv->anchored);
+        return ret;
 }
 
 static void rtl8187b_status_cb(struct urb *urb)
@@ -414,10 +434,8 @@ static void rtl8187b_status_cb(struct urb *urb)
         u64 val;
         unsigned int cmd_type;
 
-        if (unlikely(urb->status)) {
-                usb_free_urb(urb);
+        if (unlikely(urb->status))
                 return;
-        }
 
         /*
          * Read from status buffer:
@@ -488,26 +506,32 @@ static void rtl8187b_status_cb(struct urb *urb)
                 spin_unlock_irqrestore(&priv->b_tx_status.queue.lock, flags);
         }
 
-        usb_submit_urb(urb, GFP_ATOMIC);
+        usb_anchor_urb(urb, &priv->anchored);
+        if (usb_submit_urb(urb, GFP_ATOMIC))
+                usb_unanchor_urb(urb);
 }
 
 static int rtl8187b_init_status_urb(struct ieee80211_hw *dev)
 {
         struct rtl8187_priv *priv = dev->priv;
         struct urb *entry;
+        int ret = 0;
 
         entry = usb_alloc_urb(0, GFP_KERNEL);
         if (!entry)
                 return -ENOMEM;
-        priv->b_tx_status.urb = entry;
 
         usb_fill_bulk_urb(entry, priv->udev, usb_rcvbulkpipe(priv->udev, 9),
                           &priv->b_tx_status.buf, sizeof(priv->b_tx_status.buf),
                           rtl8187b_status_cb, dev);
 
-        usb_submit_urb(entry, GFP_KERNEL);
+        usb_anchor_urb(entry, &priv->anchored);
+        ret = usb_submit_urb(entry, GFP_KERNEL);
+        if (ret)
+                usb_unanchor_urb(entry);
+        usb_free_urb(entry);
 
-        return 0;
+        return ret;
 }
 
 static int rtl8187_cmd_reset(struct ieee80211_hw *dev)
@@ -841,6 +865,9 @@ static int rtl8187_start(struct ieee80211_hw *dev)
                 return ret;
 
         mutex_lock(&priv->conf_mutex);
+
+        init_usb_anchor(&priv->anchored);
+
         if (priv->is_rtl8187b) {
                 reg = RTL818X_RX_CONF_MGMT |
                       RTL818X_RX_CONF_DATA |
@@ -936,12 +963,12 @@ static void rtl8187_stop(struct ieee80211_hw *dev)
 
         while ((skb = skb_dequeue(&priv->rx_queue))) {
                 info = (struct rtl8187_rx_info *)skb->cb;
-                usb_kill_urb(info->urb);
                 kfree_skb(skb);
         }
         while ((skb = skb_dequeue(&priv->b_tx_status.queue)))
                 dev_kfree_skb_any(skb);
-        usb_kill_urb(priv->b_tx_status.urb);
+
+        usb_kill_anchored_urbs(&priv->anchored);
         mutex_unlock(&priv->conf_mutex);
 }