Subject: Re: [PATCH net] sfc: fix potential memleak in __ef100_hard_start_xmit()

From: Leon Romanovsky <[email-masked]>
Date: Thu, 17 Nov 2022 15:05:27 +0200

On Thu, Nov 17, 2022 at 08:41:52PM +0800, Zhang Changzhong wrote:
> 
> 
> On 2022/11/17 19:36, Leon Romanovsky wrote:
> > On Thu, Nov 17, 2022 at 03:50:09PM +0800, Zhang Changzhong wrote:
> >> The __ef100_hard_start_xmit() returns NETDEV_TX_OK without freeing skb
> >> in error handling case, add dev_kfree_skb_any() to fix it.
> >>
> >> Fixes: 51b35a454efd ("sfc: skeleton EF100 PF driver")
> >> Signed-off-by: Zhang Changzhong <[email-masked]>
> >> ---
> >>  drivers/net/ethernet/sfc/ef100_netdev.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/drivers/net/ethernet/sfc/ef100_netdev.c b/drivers/net/ethernet/sfc/ef100_netdev.c
> >> index 88fa295..ddcc325 100644
> >> --- a/drivers/net/ethernet/sfc/ef100_netdev.c
> >> +++ b/drivers/net/ethernet/sfc/ef100_netdev.c
> >> @@ -218,6 +218,7 @@ netdev_tx_t __ef100_hard_start_xmit(struct sk_buff *skb,
> >>  		   skb->len, skb->data_len, channel->channel);
> >>  	if (!efx->n_channels || !efx->n_tx_channels || !channel) {
> >>  		netif_stop_queue(net_dev);
> >> +		dev_kfree_skb_any(skb);
> >>  		goto err;
> >>  	}
> > 
> > ef100 doesn't release in __ef100_enqueue_skb() either. SKB shouldn't be
> > NULL or ERR at this stage.
> 
> SKB shouldn't be NULL or ERR, so it can be freed. But this code looks weird.

Please take a look __ef100_enqueue_skb() and see if it frees SKB on
error or not. If not, please fix it.

Thanks

> 
> > 
> > diff --git a/drivers/net/ethernet/sfc/ef100_tx.c b/drivers/net/ethernet/sfc/ef100_tx.c
> > index 29ffaf35559d..426706b91d02 100644
> > --- a/drivers/net/ethernet/sfc/ef100_tx.c
> > +++ b/drivers/net/ethernet/sfc/ef100_tx.c
> > @@ -497,7 +497,7 @@ int __ef100_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb,
> > 
> >  err:
> >         efx_enqueue_unwind(tx_queue, old_insert_count);
> > -       if (!IS_ERR_OR_NULL(skb))
> > +       if (rc)
> >                 dev_kfree_skb_any(skb);
> > 
> >         /* If we're not expecting another transmit and we had something to push
> > 
> > 
> >>  
> >> -- 
> >> 2.9.5
> >>
> > .
> >