Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <EED43E20-9B88-42EC-80B0-0245F0FAF980@gmail.com> <20200527133301.GL22511@kadam>
In-Reply-To: <20200527133301.GL22511@kadam>
From:   Eric Dumazet <edumazet@google.com>
Date:   Wed, 27 May 2020 09:52:14 -0700
Message-ID: <CANn89i+Pv6ANBWx-wy-aRXsPgDs=ERzumBvB2g3xiC7OfXXGwA@mail.gmail.com>
Subject: Re: [PATCH resend] airo: Fix read overflow in mpi_send_packet()
To:     Dan Carpenter <dan.carpenter@oracle.com>
Cc:     Kalle Valo <kvalo@codeaurora.org>, Hu Jiahui <kirin.say@gmail.com>,
        Security Officers <security@kernel.org>,
        linux-wireless@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

On Wed, May 27, 2020 at 6:37 AM Dan Carpenter <dan.carpenter@oracle.com> 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@vger.kernel.org>
> Reported-by: Hu Jiahui <kirin.say@gmail.com>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> 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