>From a87ff961f0a5d50223bd084dfac4fe5ce84f3913 Mon Sep 17 00:00:00 2001
From: Ming Lei <tom.leiming@xxxxxxxxx>
Date: Thu, 26 Apr 2012 11:33:46 +0800
Subject: [PATCH] usbnet: fix skb traversing races during unlink(v2)
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@xxxxxxxxx>
Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
Cc: Oliver Neukum <oneukum@xxxxxxx>
Cc: stable@xxxxxxxxxx
---
v2:
- if the Rx URB has been marked as being unlink, just not resubmit it
in complete handler, so usb_block_urb/usb_unblock_urb can be avoided,
then make backporting for -stable easier.
v1:
- fix comment style and avoiding to expose the internal
details of SKB lists, as suggested by David Miller
drivers/net/usb/usbnet.c | 54 +++++++++++++++++++++++++++++++-------------
include/linux/usb/usbnet.h | 3 ++-
2 files changed, 40 insertions(+), 17 deletions(-)
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 80b837c..9f58330 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -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;
/*
@@ -1040,8 +1064,7 @@ 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);
}
/*-------------------------------------------------------------------------*/
@@ -1097,7 +1120,6 @@ 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,
@@ -1156,7 +1178,7 @@ 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);
}
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index 605b0aa..76f4396 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -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 */
--
1.7.9.5
Thanks,
--
Ming Lei
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