2022-08-22 03:03:41

by Yang Yingliang

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

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 <[email protected]>
Signed-off-by: Yang Yingliang <[email protected]>
---
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

2022-08-22 08:03:21

by Nikolay Aleksandrov

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

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 <[email protected]>
> Signed-off-by: Yang Yingliang <[email protected]>
> ---
> 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 <[email protected]>

2022-08-24 09:34:07

by patchwork-bot+netdevbpf

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

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <[email protected]>:

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 <[email protected]>
> Signed-off-by: Yang Yingliang <[email protected]>
>
> [...]

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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