[PATCH net v2 RESEND] net: neigh: don't call kfree_skb() under spin_lock_irqsave()

[PATCH net v2 RESEND] net: neigh: don't call kfree_skb() under spin_lock_irqsave()

[Yang Yingliang]

It is not allowed to call kfree_skb() from hardware interrupt
context or with interrupts being disabled. So add all skb to
a tmp list, then free them after spin_unlock_irqrestore() at
once.

Fixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop")
Suggested-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
v2:
  move all skb to a tmp list, then free them after spin_unlock_irqrestore().
---
 net/core/neighbour.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 5b669eb80270..78cc8fb68814 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -309,14 +309,17 @@ static int neigh_del_timer(struct neighbour *n)
 
 static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net)
 {
+	struct sk_buff_head tmp;
 	unsigned long flags;
 	struct sk_buff *skb;
 
+	skb_queue_head_init(&tmp);
 	spin_lock_irqsave(&list->lock, flags);
 	skb = skb_peek(list);
 	while (skb != NULL) {
 		struct sk_buff *skb_next = skb_peek_next(skb, list);
 		struct net_device *dev = skb->dev;
+
 		if (net == NULL || net_eq(dev_net(dev), net)) {
 			struct in_device *in_dev;
 
@@ -326,13 +329,16 @@ static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net)
 				in_dev->arp_parms->qlen--;
 			rcu_read_unlock();
 			__skb_unlink(skb, list);
-
-			dev_put(dev);
-			kfree_skb(skb);
+			__skb_queue_tail(&tmp, skb);
 		}
 		skb = skb_next;
 	}
 	spin_unlock_irqrestore(&list->lock, flags);
+
+	while ((skb = __skb_dequeue(&tmp))) {
+		dev_put(skb->dev);
+		kfree_skb(skb);
+	}
 }
 
 static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev,
-- 
2.25.1

Re: [PATCH net v2 RESEND] net: neigh: don't call kfree_skb() under spin_lock_irqsave()

[Nikolay Aleksandrov]

On 22/08/2022 05:53, Yang Yingliang wrote:
> It is not allowed to call kfree_skb() from hardware interrupt
> context or with interrupts being disabled. So add all skb to
> a tmp list, then free them after spin_unlock_irqrestore() at
> once.
> 
> Fixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop")
> Suggested-by: Denis V. Lunev <den@openvz.org>
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
> v2:
>   move all skb to a tmp list, then free them after spin_unlock_irqrestore().
> ---
>  net/core/neighbour.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 

LGTM,
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>

Re: [PATCH net v2 RESEND] net: neigh: don't call kfree_skb() under spin_lock_irqsave()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Mon, 22 Aug 2022 10:53:46 +0800 you wrote:
> It is not allowed to call kfree_skb() from hardware interrupt
> context or with interrupts being disabled. So add all skb to
> a tmp list, then free them after spin_unlock_irqrestore() at
> once.
> 
> Fixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop")
> Suggested-by: Denis V. Lunev <den@openvz.org>
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> 
> [...]

Here is the summary with links:
  - [net,v2,RESEND] net: neigh: don't call kfree_skb() under spin_lock_irqsave()
    https://git.kernel.org/netdev/net/c/d5485d9dd24e

You are awesome, thank you!
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