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Date: Mon, 22 Aug 2022 09:39:21 +0800 From: Yang Yingliang <yangyingliang@...wei.com> To: Nikolay Aleksandrov <razor@...ckwall.org>, <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org> CC: <den@...nvz.org>, <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org> Subject: Re: [PATCH net v2] net: neigh: don't call kfree_skb() under spin_lock_irqsave() Hi, On 2022/8/19 20:15, Nikolay Aleksandrov wrote: > On 19/08/2022 07:47, 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") >> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com> >> --- >> 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 :q > (struct sk_buff_head *list, struct net *net) >> __skb_unlink(skb, list); >> >> dev_put(dev); >> - kfree_skb(skb); >> + dev_kfree_skb_irq(skb); > this is still doing dev_kfree_skb_irq() instead of attaching the skb to tmp, in fact > tmp seems unused so the loop below does nothing > >> } >> skb = skb_next; >> } >> spin_unlock_irqrestore(&list->lock, flags); >> + >> + while ((skb = __skb_dequeue(&tmp))) { >> + dev_put(skb->dev); > Also note that there's already a dev_put() above I made a mistake and send a wrong patch, please ignore this patch. Thanks, Yang > >> + kfree_skb(skb); >> + } >> } >> >> static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev, > > .
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