Messages in this thread | | | Subject | Re: [PATCH net] net: sonic: remove dev_kfree_skb before return NETDEV_TX_BUSY | From | Eric Dumazet <> | Date | Wed, 4 Sep 2019 12:19:51 +0200 |
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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 <maowenan@huawei.com> > --- > 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.
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