RE: [PATCH V2] hippi: fix possible buffer overflow caused by bad DMA value in rr_start_xmit()

[Sunil Kovvuri Goutham]

>The value rrpriv->info->tx_ctrl is stored in DMA memory, and it is assigned to txctrl,
>so txctrl->pi can be modified at any time by malicious hardware. Becausetxctrl->pi is
>assigned to index, buffer overflow may occur when the code "rrpriv-
>>tx_skbuff[index]" is executed.
>
>To address this issue, the index should be checked.
>
>Fixes: f33a7251c825 ("hippi: switch from 'pci_' to 'dma_' API")
>Signed-off-by: Huai-Yuan Liu <qq810974084@xxxxxxxxx>
>---
>V2:
>* In patch V2, we remove the first condition in if statement and use
>  netdev_err() instead of printk().
>  Thanks Paolo Abeni for helpful advice.
>---
> drivers/net/hippi/rrunner.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/drivers/net/hippi/rrunner.c b/drivers/net/hippi/rrunner.c index
>aa8f828a0ae7..6b0056ced922 100644
>--- a/drivers/net/hippi/rrunner.c
>+++ b/drivers/net/hippi/rrunner.c
>@@ -1440,6 +1440,11 @@ static netdev_tx_t rr_start_xmit(struct sk_buff *skb,
> 	txctrl = &rrpriv->info->tx_ctrl;
>
> 	index = txctrl->pi;
>+	if (index >= TX_RING_ENTRIES) {
>+		netdev_err(dev, "invalid index value %02x\n", index);

Much better would be to use netif_msg_tx_err which can be enabled/disabled instead of dumping on console,
which would be annoying if there are many errors.

Thanks,
Sunil.