net: add a recursion limit in xmit path
As tunnel devices are going to be lockless, we need to make sure a
misconfigured machine wont enter an infinite loop.
Add a percpu variable, and limit to three the number of stacked xmits.
Reported-by: Jesse Gross <jesse@nicira.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 48ad47f..50dacca 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2177,6 +2177,9 @@
return rc;
}
+static DEFINE_PER_CPU(int, xmit_recursion);
+#define RECURSION_LIMIT 3
+
/**
* dev_queue_xmit - transmit a buffer
* @skb: buffer to transmit
@@ -2242,10 +2245,15 @@
if (txq->xmit_lock_owner != cpu) {
+ if (__this_cpu_read(xmit_recursion) > RECURSION_LIMIT)
+ goto recursion_alert;
+
HARD_TX_LOCK(dev, txq, cpu);
if (!netif_tx_queue_stopped(txq)) {
+ __this_cpu_inc(xmit_recursion);
rc = dev_hard_start_xmit(skb, dev, txq);
+ __this_cpu_dec(xmit_recursion);
if (dev_xmit_complete(rc)) {
HARD_TX_UNLOCK(dev, txq);
goto out;
@@ -2257,7 +2265,9 @@
"queue packet!\n", dev->name);
} else {
/* Recursion is detected! It is possible,
- * unfortunately */
+ * unfortunately
+ */
+recursion_alert:
if (net_ratelimit())
printk(KERN_CRIT "Dead loop on virtual device "
"%s, fix it urgently!\n", dev->name);