[RFC][PATCH v2] p54usb: rewriting rx/tx routines to make use of usb_anchor's facilities

Christian Lamparter
2008-12-08T14:07:29Z

Alan Stern found several flaws in p54usb's implementation and annotated:
"usb_kill_urb() and similar routines do not expect an URB's completion
routine to deallocate it.  This is almost obvious -- if the URB is deallocated
before the completion routine returns then there's no way for usb_kill_urb
to detect when the URB actually is complete."

I really hope this patch addresses all of Alan's comments and fixes the
"use-after-freed" hang, when SLUB debug's poisoning option is enabled.
---
> I looked quickly at your new code. It seems basically right, but there
> are few things that still need attention. For instance, you removed a
> line to free an URB's transfer buffer.

yeah, it was there in the last patch, but probably in the wrong place.
Anyway, there's now a small comment so it's easier to spot it.

So here's the new "final" version, unless someone files a complain within 24 hours.
---
diff -Nurp a/drivers/net/wireless/p54/p54usb.c b/drivers/net/wireless/p54/p54usb.c
--- a/drivers/net/wireless/p54/p54usb.c 2008-12-07 21:21:04.017774898 +0100
+++ b/drivers/net/wireless/p54/p54usb.c 2008-12-08 14:17:51.863521490 +0100
@@ -86,13 +86,13 @@ static void p54u_rx_cb(struct urb *urb)
struct ieee80211_hw *dev = info->dev;
struct p54u_priv *priv = dev->priv;

+ skb_unlink(skb, &priv->rx_queue);
+
if (unlikely(urb->status)) {
- info->urb = NULL;
- usb_free_urb(urb);
+ dev_kfree_skb_irq(skb);
return;
}

- skb_unlink(skb, &priv->rx_queue);
skb_put(skb, urb->actual_length);

if (priv->hw_type == P54U_NET2280)
@@ -105,7 +105,6 @@ static void p54u_rx_cb(struct urb *urb)
if (p54_rx(dev, skb)) {
skb = dev_alloc_skb(priv->common.rx_mtu + 32);
if (unlikely(!skb)) {
- usb_free_urb(urb);
/* TODO check rx queue length and refill *somewhere* */
return;
}
@@ -115,7 +114,6 @@ static void p54u_rx_cb(struct urb *urb)
info->dev = dev;
urb->transfer_buffer = skb_tail_pointer(skb);
urb->context = skb;
- skb_queue_tail(&priv->rx_queue, skb);
} else {
if (priv->hw_type == P54U_NET2280)
skb_push(skb, priv->common.tx_hdr_len);
@@ -130,11 +128,14 @@ static void p54u_rx_cb(struct urb *urb)
WARN_ON(1);
urb->transfer_buffer = skb_tail_pointer(skb);
}
-
- skb_queue_tail(&priv->rx_queue, skb);
}
-
- usb_submit_urb(urb, GFP_ATOMIC);
+ skb_queue_tail(&priv->rx_queue, skb);
+ usb_anchor_urb(urb, &priv->submitted);
+ if (usb_submit_urb(urb, GFP_ATOMIC)) {
+ skb_unlink(skb, &priv->rx_queue);
+ usb_unanchor_urb(urb);
+ dev_kfree_skb_irq(skb);
+ }
}

static void p54u_tx_reuse_skb_cb(struct urb *urb)
@@ -144,18 +145,6 @@ static void p54u_tx_reuse_skb_cb(struct
usb_get_intfdata(usb_ifnum_to_if(urb->dev, 0)))->priv;

skb_pull(skb, priv->common.tx_hdr_len);
- usb_free_urb(urb);
-}
-
-static void p54u_tx_cb(struct urb *urb)
-{
- usb_free_urb(urb);
-}
-
-static void p54u_tx_free_cb(struct urb *urb)
-{
- kfree(urb->transfer_buffer);
- usb_free_urb(urb);
}

static void p54u_tx_free_skb_cb(struct urb *urb)
@@ -165,25 +154,36 @@ static void p54u_tx_free_skb_cb(struct u
usb_get_intfdata(usb_ifnum_to_if(urb->dev, 0));

p54_free_skb(dev, skb);
- usb_free_urb(urb);
+}
+
+static void p54u_tx_dummy_cb(struct urb *urb) { }
+
+static void p54u_free_urbs(struct ieee80211_hw *dev)
+{
+ struct p54u_priv *priv = dev->priv;
+ usb_kill_anchored_urbs(&priv->submitted);
}

static int p54u_init_urbs(struct ieee80211_hw *dev)
{
struct p54u_priv *priv = dev->priv;
- struct urb *entry;
+ struct urb *entry = NULL;
struct sk_buff *skb;
struct p54u_rx_info *info;
+ int ret = 0;

while (skb_queue_len(&priv->rx_queue) < 32) {
skb = __dev_alloc_skb(priv->common.rx_mtu + 32, 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, P54U_PIPE_DATA),
skb_tail_pointer(skb),
@@ -192,26 +192,25 @@ static int p54u_init_urbs(struct ieee802
info->urb = entry;
info->dev = dev;
skb_queue_tail(&priv->rx_queue, skb);
- usb_submit_urb(entry, GFP_KERNEL);
+
+ usb_anchor_urb(entry, &priv->submitted);
+ 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);
+ entry = NULL;
}

return 0;
-}

-static void p54u_free_urbs(struct ieee80211_hw *dev)
-{
- struct p54u_priv *priv = dev->priv;
- struct p54u_rx_info *info;
- struct sk_buff *skb;
-
- while ((skb = skb_dequeue(&priv->rx_queue))) {
- info = (struct p54u_rx_info *) skb->cb;
- if (!info->urb)
- continue;
-
- usb_kill_urb(info->urb);
- kfree_skb(skb);
- }
+ err:
+ usb_free_urb(entry);
+ kfree_skb(skb);
+ p54u_free_urbs(dev);
+ return ret;
}

static void p54u_tx_3887(struct ieee80211_hw *dev, struct sk_buff *skb,
@@ -219,6 +218,7 @@ static void p54u_tx_3887(struct ieee8021
{
struct p54u_priv *priv = dev->priv;
struct urb *addr_urb, *data_urb;
+ int err = 0;

addr_urb = usb_alloc_urb(0, GFP_ATOMIC);
if (!addr_urb)
@@ -233,15 +233,31 @@ static void p54u_tx_3887(struct ieee8021
usb_fill_bulk_urb(addr_urb, priv->udev,
usb_sndbulkpipe(priv->udev, P54U_PIPE_DATA),
&((struct p54_hdr *)skb->data)->req_id, 4,
- p54u_tx_cb, dev);
+ p54u_tx_dummy_cb, dev);
usb_fill_bulk_urb(data_urb, priv->udev,
usb_sndbulkpipe(priv->udev, P54U_PIPE_DATA),
skb->data, skb->len,
free_on_tx ? p54u_tx_free_skb_cb :
p54u_tx_reuse_skb_cb, skb);

- usb_submit_urb(addr_urb, GFP_ATOMIC);
- usb_submit_urb(data_urb, GFP_ATOMIC);
+ usb_anchor_urb(addr_urb, &priv->submitted);
+ err = usb_submit_urb(addr_urb, GFP_ATOMIC);
+ if (err) {
+ usb_unanchor_urb(addr_urb);
+ goto out;
+ }
+
+ usb_anchor_urb(addr_urb, &priv->submitted);
+ err = usb_submit_urb(data_urb, GFP_ATOMIC);
+ if (err)
+ usb_unanchor_urb(data_urb);
+
+ out:
+ usb_free_urb(addr_urb);
+ usb_free_urb(data_urb);
+
+ if (err)
+ p54_free_skb(dev, skb);
}

static __le32 p54u_lm87_chksum(const __le32 *data, size_t length)
@@ -281,7 +297,13 @@ static void p54u_tx_lm87(struct ieee8021
free_on_tx ? p54u_tx_free_skb_cb :
p54u_tx_reuse_skb_cb, skb);

- usb_submit_urb(data_urb, GFP_ATOMIC);
+ usb_anchor_urb(data_urb, &priv->submitted);
+ if (usb_submit_urb(data_urb, GFP_ATOMIC)) {
+ usb_unanchor_urb(data_urb);
+ skb_pull(skb, sizeof(*hdr));
+ p54_free_skb(dev, skb);
+ }
+ usb_free_urb(data_urb);
}

static void p54u_tx_net2280(struct ieee80211_hw *dev, struct sk_buff *skb,
@@ -291,6 +313,7 @@ static void p54u_tx_net2280(struct ieee8
struct urb *int_urb, *data_urb;
struct net2280_tx_hdr *hdr;
struct net2280_reg_write *reg;
+ int err = 0;

reg = kmalloc(sizeof(*reg), GFP_ATOMIC);
if (!reg)
@@ -320,15 +343,42 @@ static void p54u_tx_net2280(struct ieee8

usb_fill_bulk_urb(int_urb, priv->udev,
usb_sndbulkpipe(priv->udev, P54U_PIPE_DEV), reg, sizeof(*reg),
- p54u_tx_free_cb, dev);
- usb_submit_urb(int_urb, GFP_ATOMIC);
+ p54u_tx_dummy_cb, dev);
+
+ /*
+ * This flag triggers a code path in the USB subsystem that will
+ * free what's inside the transfer_buffer after the callback routine
+ * has completed.
+ */
+ int_urb->transfer_flags |= URB_FREE_BUFFER;

usb_fill_bulk_urb(data_urb, priv->udev,
usb_sndbulkpipe(priv->udev, P54U_PIPE_DATA),
skb->data, skb->len,
free_on_tx ? p54u_tx_free_skb_cb :
p54u_tx_reuse_skb_cb, skb);
- usb_submit_urb(data_urb, GFP_ATOMIC);
+
+ usb_anchor_urb(int_urb, &priv->submitted);
+ err = usb_submit_urb(int_urb, GFP_ATOMIC);
+ if (err) {
+ usb_unanchor_urb(int_urb);
+ goto out;
+ }
+
+ usb_anchor_urb(data_urb, &priv->submitted);
+ err = usb_submit_urb(data_urb, GFP_ATOMIC);
+ if (err) {
+ usb_unanchor_urb(data_urb);
+ goto out;
+ }
+ out:
+ usb_free_urb(int_urb);
+ usb_free_urb(data_urb);
+
+ if (err) {
+ skb_pull(skb, sizeof(*hdr));
+ p54_free_skb(dev, skb);
+ }
}

static int p54u_write(struct p54u_priv *priv,
@@ -886,6 +936,7 @@ static int __devinit p54u_probe(struct u
goto err_free_dev;

skb_queue_head_init(&priv->rx_queue);
+ init_usb_anchor(&priv->submitted);

p54u_open(dev);
err = p54_read_eeprom(dev);
diff -Nurp a/drivers/net/wireless/p54/p54usb.h b/drivers/net/wireless/p54/p54usb.h
--- a/drivers/net/wireless/p54/p54usb.h 2008-12-07 21:21:04.017774898 +0100
+++ b/drivers/net/wireless/p54/p54usb.h 2008-12-07 22:04:45.956897502 +0100
@@ -133,6 +133,7 @@ struct p54u_priv {

spinlock_t lock;
struct sk_buff_head rx_queue;
+ struct usb_anchor submitted;
};

#endif /* P54USB_H */