[PATCH V3] hippi: fix possible buffer overflow caused by bad DMA value in rr_start_xmit()

[PATCH V3] hippi: fix possible buffer overflow caused by bad DMA value in rr_start_xmit()

[Huai-Yuan Liu]

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@gmail.com>
---
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.
V3:
* In patch V3, we stop the queue before return BUSY.
  Thanks to Jakub Kicinski for his advice.
---
 drivers/net/hippi/rrunner.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/hippi/rrunner.c b/drivers/net/hippi/rrunner.c
index aa8f828a0ae7..f4da342dd5cc 100644
--- a/drivers/net/hippi/rrunner.c
+++ b/drivers/net/hippi/rrunner.c
@@ -1440,6 +1440,12 @@ 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);
+		netif_stop_queue(dev);
+		spin_unlock_irqrestore(&rrpriv->lock, flags);
+		return NETDEV_TX_BUSY;
+	}
 
 	rrpriv->tx_skbuff[index] = skb;
 	set_rraddr(&rrpriv->tx_ring[index].addr,
-- 
2.34.1

Re: [PATCH V3] hippi: fix possible buffer overflow caused by bad DMA value in rr_start_xmit()

[Markus Elfring]

> …. Becausetxctrl->pi is assigned to …

     Word separation?


> To address this issue, the index should be checked.

Can an imperative wording be more desirable for such a change description?
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.10-rc4#n94

Regards,
Markus