On Wed, May 27, 2020 at 6:37 AM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> The problem is that we always copy a minimum of ETH_ZLEN (60) bytes from
> skb->data even when skb->len is less than ETH_ZLEN so it leads to a read
> overflow.
>
> The fix for is to pad skb->data with zeroes so that it's never less than
> ETH_ZLEN bytes.
>
> c: <stable@xxxxxxxxxxxxxxx>
> Reported-by: Hu Jiahui <kirin.say@xxxxxxxxx>
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> Resending to the public lists so that it can go through the normal
> review process.
>
> My other concern with this driver is why is the ->max_mtu 2400 when it
> looks like we are allocating PKTSIZE (1840) byte buffers to hold it in
> mpi_map_card()? I don't fully understand the code but that seems like
> it could be a buffer overflow as well. I'm not sure what the
> appropriate fix is for that.
>
> drivers/net/wireless/cisco/airo.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/cisco/airo.c b/drivers/net/wireless/cisco/airo.c
> index 8363f91df7ea7..7c5634f72cc72 100644
> --- a/drivers/net/wireless/cisco/airo.c
> +++ b/drivers/net/wireless/cisco/airo.c
> @@ -1925,6 +1925,11 @@ static netdev_tx_t mpi_start_xmit(struct sk_buff *skb,
> airo_print_err(dev->name, "%s: skb == NULL!",__func__);
> return NETDEV_TX_OK;
> }
> + if (skb->len < ETH_ZLEN) {
No need to duplicate the test.
Just use
if (skb_padto(skb, ETH_ZLEN)) {
dev->stats.tx_dropped++;
return NETDEV_TX_OK;
}
> + if (skb_padto(skb, ETH_ZLEN))
> + return NETDEV_TX_OK;
> + }
> +
> npacks = skb_queue_len (&ai->txq);
>
> if (npacks >= MAXTXQ - 1) {
> @@ -1975,8 +1980,7 @@ static int mpi_send_packet (struct net_device *dev)
> return 0;
> }
>
> - /* check min length*/
> - len = ETH_ZLEN < skb->len ? skb->len : ETH_ZLEN;
> + len = skb->len;
> buffer = skb->data;
>
> ai->txfids[0].tx_desc.offset = 0;
> --
> 2.26.2
