[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date: Mon, 7 Jun 2021 00:25:17 +0200
From: Hauke Mehrtens <hauke@...ke-m.de>
To: Aleksander Jan Bajkowski <olek2@...pl>, davem@...emloft.net,
kuba@...nel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] lantiq: net: fix duplicated skb in rx descriptor ring
On 6/6/21 10:05 PM, Aleksander Jan Bajkowski wrote:
> The previous commit didn't fix the bug properly. By mistake, it replaces
> the pointer of the next skb in the descriptor ring instead of the current
> one. As a result, the two descriptors are assigned the same SKB. The error
> is seen during the iperf test when skb_put tries to insert a second packet
> and exceeds the available buffer.
>
> Fixes: c7718ee96dbc ("net: lantiq: fix memory corruption in RX ring ")
>
> Signed-off-by: Aleksander Jan Bajkowski <olek2@...pl>
> ---
> drivers/net/ethernet/lantiq_xrx200.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
> index 36dc3e5f6218..e710f83b3700 100644
> --- a/drivers/net/ethernet/lantiq_xrx200.c
> +++ b/drivers/net/ethernet/lantiq_xrx200.c
> @@ -193,17 +193,18 @@ static int xrx200_hw_receive(struct xrx200_chan *ch)
> int ret;
>
> ret = xrx200_alloc_skb(ch);
> -
> - ch->dma.desc++;
> - ch->dma.desc %= LTQ_DESC_NUM;
> -
> if (ret) {
> ch->skb[ch->dma.desc] = skb;
> net_dev->stats.rx_dropped++;
> + ch->dma.desc++;
> + ch->dma.desc %= LTQ_DESC_NUM;
I would prefer if you handle this problem in the xrx200_alloc_skb()
function.
You could also provide the skb to xrx200_alloc_skb() and use it in case
a problem occurs, you would loose the current received packet, but the
DMA ring stays valid.
An other solution would be to not set LTQ_DMA_OWN, then the DMA hardware
will not use this memory, but we have to handle it somewhere else.
I am also not sure if the wmb() is needed, the desc_base was allocated
with dma_alloc_coherent(), I assume that the changes are directly
written to the memory and not reordered.
> netdev_err(net_dev, "failed to allocate new rx buffer\n");
> return ret;
> }
>
> + ch->dma.desc++;
> + ch->dma.desc %= LTQ_DESC_NUM;
> +
> skb_put(skb, len);
> skb->protocol = eth_type_trans(skb, net_dev);
> netif_receive_skb(skb);
>
Download attachment "OpenPGP_0x93DD20630910B515.asc" of type "application/pgp-keys" (9896 bytes)
Download attachment "OpenPGP_signature" of type "application/pgp-signature" (489 bytes)
Powered by blists - more mailing lists