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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 <jesse@nicira.com>
Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ab79ad14

net/core/dev.c

+11 −1
Original line number Diff line number Diff line
@@ -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);

#define RECURSION_LIMIT 3



/**

 *	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)) {

				__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 @@ int dev_queue_xmit(struct sk_buff *skb) 
				       "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);