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

From: Yang Yingliang
Date: Fri Aug 19 2022 - 00:39:25 EST


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,
--
2.25.1