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

From: Martin Habets <[email-masked]>
Date: Fri, 18 Nov 2022 09:15:43 +0000

On Thu, Nov 17, 2022 at 03:05:27PM +0200, Leon Romanovsky wrote:
> 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.

That function looks ok to me, but I appreciate the extra eyes on it.

Martin

> 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
> > >>
> > > .
> > >