netdev - Re: [PATCH] rtl8xxxu: avoid parsing short RX packet

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Date:   Tue, 1 Jun 2021 10:57:41 +0200
From:   Íñigo Huguet <ihuguet@...hat.com>
To:     Jes.Sorensen@...il.com, kvalo@...eaurora.org
Cc:     davem@...emloft.net, kuba@...nel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] rtl8xxxu: avoid parsing short RX packet

On Tue, May 11, 2021 at 9:19 AM Íñigo Huguet <ihuguet@...hat.com> wrote:
>
> One USB data buffer can contain multiple received network
> packets. If that's the case, they're processed this way:
> 1. Original buffer is cloned
> 2. Original buffer is trimmed to contain only the first
>    network packet
> 3. This first network packet is passed to network stack
> 4. Cloned buffer is trimmed to eliminate the first network
>    packet
> 5. Repeat with the cloned buffer until there are no more
>    network packets inside
>
> However, if the space remaining in original buffer after
> the first network packet is not enough to contain at least
> another network packet descriptor, it is not cloned.
>
> The loop parsing this packets ended if remaining space == 0.
> But if the remaining space was > 0 but < packet descriptor
> size, another iteration of the loop was done, processing again
> the previous packet because cloning didn't happen. Moreover,
> the ownership of this packet had been passed to network
> stack in the previous iteration.
>
> This patch ensures that no extra iteration is done if the
> remaining size is not enough for one packet, and also avoid
> the first iteration for the same reason.
>
> Probably this doesn't happen in practice, but can happen
> theoretically.
>
> Signed-off-by: Íñigo Huguet <ihuguet@...hat.com>
> ---
>  drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> index 9ff09cf7eb62..673961a82c40 100644
> --- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> +++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> @@ -5554,6 +5554,11 @@ int rtl8xxxu_parse_rxdesc16(struct rtl8xxxu_priv *priv, struct sk_buff *skb)
>         urb_len = skb->len;
>         pkt_cnt = 0;
>
> +       if (urb_len < sizeof(struct rtl8xxxu_rxdesc16)) {
> +               kfree_skb(skb);
> +               return RX_TYPE_ERROR;
> +       }
> +
>         do {
>                 rx_desc = (struct rtl8xxxu_rxdesc16 *)skb->data;
>                 _rx_desc_le = (__le32 *)skb->data;
> @@ -5581,7 +5586,7 @@ int rtl8xxxu_parse_rxdesc16(struct rtl8xxxu_priv *priv, struct sk_buff *skb)
>                  * at least cover the rx descriptor
>                  */
>                 if (pkt_cnt > 1 &&
> -                   urb_len > (pkt_offset + sizeof(struct rtl8xxxu_rxdesc16)))
> +                   urb_len >= (pkt_offset + sizeof(struct rtl8xxxu_rxdesc16)))
>                         next_skb = skb_clone(skb, GFP_ATOMIC);
>
>                 rx_status = IEEE80211_SKB_RXCB(skb);
> @@ -5627,7 +5632,9 @@ int rtl8xxxu_parse_rxdesc16(struct rtl8xxxu_priv *priv, struct sk_buff *skb)
>
>                 pkt_cnt--;
>                 urb_len -= pkt_offset;
> -       } while (skb && urb_len > 0 && pkt_cnt > 0);
> +               next_skb = NULL;
> +       } while (skb && pkt_cnt > 0 &&
> +                urb_len >= sizeof(struct rtl8xxxu_rxdesc16));
>
>         return RX_TYPE_DATA_PKT;
>  }
> --
> 2.31.1
>

Hello,

About 3 weeks ago I sent this patch, but received no response. Any
feedback would be appreciated.

Thanks!
-- 
Íñigo Huguet