2022-08-19 05:18:36

by Yang Yingliang

Subject: [PATCH net v2] 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")
Signed-off-by: Yang Yingliang <[email protected]>
---
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

2022-08-19 08:33:51

by Denis V. Lunev

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

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 <[email protected]>
> ---
> 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 <[email protected]>

2022-08-19 12:46:16

by Nikolay Aleksandrov

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

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 <[email protected]>
> ---
> 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

> + kfree_skb(skb);
> + }
> }
>
> static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev,

2022-08-22 01:45:32

by Yang Yingliang

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 <[email protected]>
>> ---
>> 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,
>
> .