Commit 745e20f1 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarJesse Gross <>
Signed-off-by: default avatarEric Dumazet <>
Signed-off-by: default avatarDavid S. Miller <>
parent ab79ad14
......@@ -2177,6 +2177,9 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
return rc;
static DEFINE_PER_CPU(int, xmit_recursion);
* dev_queue_xmit - transmit a buffer
* @skb: buffer to transmit
......@@ -2242,10 +2245,15 @@ int dev_queue_xmit(struct sk_buff *skb)
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)) {
rc = dev_hard_start_xmit(skb, dev, txq);
if (dev_xmit_complete(rc)) {
HARD_TX_UNLOCK(dev, txq);
goto out;
......@@ -2257,7 +2265,9 @@ int dev_queue_xmit(struct sk_buff *skb)
"queue packet!\n", dev->name);
} else {
/* Recursion is detected! It is possible,
* unfortunately */
* unfortunately
if (net_ratelimit())
printk(KERN_CRIT "Dead loop on virtual device "
"%s, fix it urgently!\n", dev->name);
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