Skip to content

Commit

Permalink
usbnet: fix skb traversing races during unlink(v2)
Browse files Browse the repository at this point in the history 
Commit 4231d47(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>
  • Loading branch information
Ming Lei authored and David S. Miller committed May 15, 2012
1 parent 8aa51d6 commit 5b6e9bc
Show file tree
Hide file tree
Showing 2 changed files with 40 additions and 17 deletions.
54 changes: 38 additions & 16 deletions drivers/net/usb/usbnet.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -282,24 +282,40 @@ 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);
__skb_queue_tail(&dev->done, skb);
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
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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");
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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;
Expand All @@ -482,17 +498,18 @@ static void rx_complete (struct urb *urb)
// 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;
Expand Down Expand Up @@ -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;

/*
Expand Down Expand Up @@ -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);
}

/*-------------------------------------------------------------------------*/
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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);
}
Expand Down
3 changes: 2 additions & 1 deletion include/linux/usb/usbnet.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand Down

0 comments on commit 5b6e9bc

Please sign in to comment.