Re: [PATCH net] net: sonic: remove dev_kfree_skb before return NETDEV_TX_BUSY

2019-09-04 Thread maowenan 



On 2019/9/4 18:19, Eric Dumazet wrote:
> 
> 
> On 9/4/19 11:42 AM, Mao Wenan wrote:
>> When dma_map_single is failed to map buffer, skb can't be freed
>> before sonic driver return to stack with NETDEV_TX_BUSY, because
>> this skb may be requeued to qdisc, it might trigger use-after-free.
>>
>> Fixes: d9fb9f384292 ("*sonic/natsemi/ns83829: Move the National 
>> Semi-conductor drivers")
>> Signed-off-by: Mao Wenan 
>> ---
>>  drivers/net/ethernet/natsemi/sonic.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/natsemi/sonic.c 
>> b/drivers/net/ethernet/natsemi/sonic.c
>> index d0a01e8f000a..248a8f22a33b 100644
>> --- a/drivers/net/ethernet/natsemi/sonic.c
>> +++ b/drivers/net/ethernet/natsemi/sonic.c
>> @@ -233,7 +233,6 @@ static int sonic_send_packet(struct sk_buff *skb, struct 
>> net_device *dev)
>>  laddr = dma_map_single(lp->device, skb->data, length, DMA_TO_DEVICE);
>>  if (!laddr) {
>>  printk(KERN_ERR "%s: failed to map tx DMA buffer.\n", 
>> dev->name);
>> -dev_kfree_skb(skb);
>>  return NETDEV_TX_BUSY;
>>  }
>>  
>>
> 
> That is the wrong way to fix this bug.
> 
> What guarantee do we have that the mapping operation will succeed next time 
> we attempt
> the transmit (and the dma_map_single() operation) ?
> 
> NETDEV_TX_BUSY is very dangerous, this might trigger an infinite loop.
> 
> I would rather leave the dev_kfree_skb(skb), and return NETDEV_TX_OK
yes, right, it will go to infinite loop if dma_map_single failed always.
v2 will be sent later.
> 
> Also the printk(KERN_ERR ...) should be replaced by pr_err_ratelimited(...)
> 
> NETDEV_TX_BUSY really should only be used by drivers that call 
> netif_tx_stop_queue()
> at the wrong moment.
It will call netif_tx_stop_queue() then return NETDEV_TX_BUSY, and give a 
chance to
netif_tx_wake_queue(), then stack can be resent packet to driver?

> 
> .
>

Re: [PATCH net] net: sonic: remove dev_kfree_skb before return NETDEV_TX_BUSY

2019-09-04 Thread Eric Dumazet 



On 9/4/19 11:42 AM, Mao Wenan wrote:
> When dma_map_single is failed to map buffer, skb can't be freed
> before sonic driver return to stack with NETDEV_TX_BUSY, because
> this skb may be requeued to qdisc, it might trigger use-after-free.
> 
> Fixes: d9fb9f384292 ("*sonic/natsemi/ns83829: Move the National 
> Semi-conductor drivers")
> Signed-off-by: Mao Wenan 
> ---
>  drivers/net/ethernet/natsemi/sonic.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/natsemi/sonic.c 
> b/drivers/net/ethernet/natsemi/sonic.c
> index d0a01e8f000a..248a8f22a33b 100644
> --- a/drivers/net/ethernet/natsemi/sonic.c
> +++ b/drivers/net/ethernet/natsemi/sonic.c
> @@ -233,7 +233,6 @@ static int sonic_send_packet(struct sk_buff *skb, struct 
> net_device *dev)
>   laddr = dma_map_single(lp->device, skb->data, length, DMA_TO_DEVICE);
>   if (!laddr) {
>   printk(KERN_ERR "%s: failed to map tx DMA buffer.\n", 
> dev->name);
> - dev_kfree_skb(skb);
>   return NETDEV_TX_BUSY;
>   }
>  
> 

That is the wrong way to fix this bug.

What guarantee do we have that the mapping operation will succeed next time we 
attempt
the transmit (and the dma_map_single() operation) ?

NETDEV_TX_BUSY is very dangerous, this might trigger an infinite loop.

I would rather leave the dev_kfree_skb(skb), and return NETDEV_TX_OK

Also the printk(KERN_ERR ...) should be replaced by pr_err_ratelimited(...)

NETDEV_TX_BUSY really should only be used by drivers that call 
netif_tx_stop_queue()
at the wrong moment.

Re: [PATCH net] net: sonic: remove dev_kfree_skb before return NETDEV_TX_BUSY

2019-09-04 Thread Thomas Bogendoerfer 
On Wed, Sep 04, 2019 at 05:42:11PM +0800, Mao Wenan wrote:
> When dma_map_single is failed to map buffer, skb can't be freed
> before sonic driver return to stack with NETDEV_TX_BUSY, because
> this skb may be requeued to qdisc, it might trigger use-after-free.
> 
> Fixes: d9fb9f384292 ("*sonic/natsemi/ns83829: Move the National 
> Semi-conductor drivers")
> Signed-off-by: Mao Wenan 
> ---
>  drivers/net/ethernet/natsemi/sonic.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/natsemi/sonic.c 
> b/drivers/net/ethernet/natsemi/sonic.c
> index d0a01e8f000a..248a8f22a33b 100644
> --- a/drivers/net/ethernet/natsemi/sonic.c
> +++ b/drivers/net/ethernet/natsemi/sonic.c
> @@ -233,7 +233,6 @@ static int sonic_send_packet(struct sk_buff *skb, struct 
> net_device *dev)
>   laddr = dma_map_single(lp->device, skb->data, length, DMA_TO_DEVICE);
>   if (!laddr) {
>   printk(KERN_ERR "%s: failed to map tx DMA buffer.\n", 
> dev->name);
> - dev_kfree_skb(skb);
>   return NETDEV_TX_BUSY;
>   }

Reviewed-by: Thomas Bogendoerfer 

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.[ RFC1925, 2.3 ]

[PATCH net] net: sonic: remove dev_kfree_skb before return NETDEV_TX_BUSY

2019-09-04 Thread Mao Wenan 
When dma_map_single is failed to map buffer, skb can't be freed
before sonic driver return to stack with NETDEV_TX_BUSY, because
this skb may be requeued to qdisc, it might trigger use-after-free.

Fixes: d9fb9f384292 ("*sonic/natsemi/ns83829: Move the National Semi-conductor 
drivers")
Signed-off-by: Mao Wenan 
---
 drivers/net/ethernet/natsemi/sonic.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/ethernet/natsemi/sonic.c 
b/drivers/net/ethernet/natsemi/sonic.c
index d0a01e8f000a..248a8f22a33b 100644
--- a/drivers/net/ethernet/natsemi/sonic.c
+++ b/drivers/net/ethernet/natsemi/sonic.c
@@ -233,7 +233,6 @@ static int sonic_send_packet(struct sk_buff *skb, struct 
net_device *dev)
laddr = dma_map_single(lp->device, skb->data, length, DMA_TO_DEVICE);
if (!laddr) {
printk(KERN_ERR "%s: failed to map tx DMA buffer.\n", 
dev->name);
-   dev_kfree_skb(skb);
return NETDEV_TX_BUSY;
}
 
-- 
2.20.1