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

[Denis V. Lunev]

On 19.08.2022 06:47, 'Yang Yingliang' via den 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")
> Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
> ---
>   net/core/neighbour.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 5b669eb80270..d21c7de1ff1a 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;
>   
> @@ -328,11 +331,16 @@ static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net)
>   			__skb_unlink(skb, list);
>   
>   			dev_put(dev);
> -			kfree_skb(skb);
> +			dev_kfree_skb_irq(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,
Reviewed-by: Denis V. Lunev <den@xxxxxxxxxx>