net: usbnet: prevent buggy devices from killing us

A device sending 0 length frames as fast as it can has been
observed killing the host system due to the resulting memory
pressure.

Temporarily disable RX skb allocation and URB submission when
the current error ratio is high, preventing us from trying to
allocate an infinite number of skbs.  Reenable as soon as we
are finished processing the done queue, allowing the device
to continue working after short error bursts.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Acked-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 27 insertions, 0 deletions

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index f34b2ebee815..977837725726 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -380,6 +380,12 @@ static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
         unsigned long           lockflags;
         size_t                  size = dev->rx_urb_size;
 
+        /* prevent rx skb allocation when error ratio is high */
+        if (test_bit(EVENT_RX_KILL, &dev->flags)) {
+                usb_free_urb(urb);
+                return -ENOLINK;
+        }
+
         skb = __netdev_alloc_skb_ip_align(dev->net, size, flags);
         if (!skb) {
                 netif_dbg(dev, rx_err, dev->net, "no rx skb\n");
@@ -539,6 +545,17 @@ block:
                 break;
         }
 
+        /* stop rx if packet error rate is high */
+        if (++dev->pkt_cnt > 30) {
+                dev->pkt_cnt = 0;
+                dev->pkt_err = 0;
+        } else {
+                if (state == rx_cleanup)
+                        dev->pkt_err++;
+                if (dev->pkt_err > 20)
+                        set_bit(EVENT_RX_KILL, &dev->flags);
+        }
+
         state = defer_bh(dev, skb, &dev->rxq, state);
 
         if (urb) {
@@ -791,6 +808,11 @@ int usbnet_open (struct net_device *net)
                    (dev->driver_info->flags & FLAG_FRAMING_AX) ? "ASIX" :
                    "simple");
 
+        /* reset rx error state */
+        dev->pkt_cnt = 0;
+        dev->pkt_err = 0;
+        clear_bit(EVENT_RX_KILL, &dev->flags);
+
         // delay posting reads until we're fully open
         tasklet_schedule (&dev->bh);
         if (info->manage_power) {
@@ -1254,6 +1276,9 @@ static void usbnet_bh (unsigned long param)
                 }
         }
 
+        /* restart RX again after disabling due to high error rate */
+        clear_bit(EVENT_RX_KILL, &dev->flags);
+
         // waiting for all pending urbs to complete?
         if (dev->wait) {
                 if ((dev->txq.qlen + dev->rxq.qlen + dev->done.qlen) == 0) {
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index 5de7a220e986..0de078d4cdb9 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -33,6 +33,7 @@ struct usbnet {
         wait_queue_head_t       *wait;
         struct mutex            phy_mutex;
         unsigned char           suspend_count;
+        unsigned char           pkt_cnt, pkt_err;
 
         /* i/o info: pipes etc */
         unsigned                in, out;
@@ -70,6 +71,7 @@ struct usbnet {
 #               define EVENT_DEV_OPEN   7
 #               define EVENT_DEVICE_REPORT_IDLE 8
 #               define EVENT_NO_RUNTIME_PM      9
+#               define EVENT_RX_KILL    10
 };
 
 static inline struct usb_driver *driver_of(struct usb_interface *intf)