From 745e20f1b626b1be4b100af5d4bf7b3439392f8f Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 29 Sep 2010 13:23:09 -0700 Subject: [PATCH] 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 Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/dev.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) 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 @@ 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); -- 2.7.4