Re: [PATCH net] net: nixge: fix potential memory leak in nixge_start_xmit()

[Saeed Mahameed]

On 15 Nov 21:20, Zhang Changzhong wrote:
> On 2022/11/14 18:40, Francois Romieu wrote:
> > Zhang Changzhong <zhangchangzhong@xxxxxxxxxx> :
> > > The nixge_start_xmit() returns NETDEV_TX_OK but does not free skb on two
> > > error handling cases, which can lead to memory leak.
> > >
> > > To fix this, return NETDEV_TX_BUSY in case of nixge_check_tx_bd_space()
> > > fails and add dev_kfree_skb_any() in case of dma_map_single() fails.
> >
> > This patch merge two unrelated changes. Please split.
> >
> > > Fixes: 492caffa8a1a ("net: ethernet: nixge: Add support for National Instruments XGE netdev")
> > > Signed-off-by: Zhang Changzhong <zhangchangzhong@xxxxxxxxxx>
> > > ---
> > >  drivers/net/ethernet/ni/nixge.c | 6 ++++--
> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/ni/nixge.c b/drivers/net/ethernet/ni/nixge.c
> > > index 19d043b593cc..b9091f9bbc77 100644
> > > --- a/drivers/net/ethernet/ni/nixge.c
> > > +++ b/drivers/net/ethernet/ni/nixge.c
> > > @@ -521,13 +521,15 @@ static netdev_tx_t nixge_start_xmit(struct sk_buff *skb,
> > >  	if (nixge_check_tx_bd_space(priv, num_frag)) {
> > >  		if (!netif_queue_stopped(ndev))
> > >  			netif_stop_queue(ndev);
> > > -		return NETDEV_TX_OK;
> > > +		return NETDEV_TX_BUSY;
> > >  	}
> >
> > The driver should probably check the available room before returning
> > from hard_start_xmit and turn the check above unlikely().
> >
> > Btw there is no lock and the Tx completion is irq driven: the driver
> > is racy. :o(
>
> Hi Francois,
>
> Thanks for you review. I'll make v2 according to your suggestion.

you will probably need to check out: Transmit path guidelines:
https://www.kernel.org/doc/Documentation/networking/driver.rst