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

From: Saeed Mahameed
Date: Wed Nov 16 2022 - 17:36:27 EST


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