net: dsa: tag_rtl4_a: fix egress tags

Commit 86dd9868b878 has several issues, but was accepted too soon
before anyone could take a look.

- Double free. dsa_slave_xmit() will free the skb if the xmit function
  returns NULL, but the skb is already freed by eth_skb_pad(). Use
  __skb_put_padto() to avoid that.
- Unnecessary allocation. It has been done by DSA core since commit
  a3b0b6479700.
- A u16 pointer points to skb data. It should be __be16 for network
  byte order.
- Typo in comments. "numer" -> "number".

Fixes: 86dd9868b878 ("net: dsa: tag_rtl4_a: Support also egress tags")
Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/dsa/tag_rtl4_a.c b/net/dsa/tag_rtl4_a.c
index c17d39b..e917647 100644 (file)
--- a/net/dsa/tag_rtl4_a.c
+++ b/net/dsa/tag_rtl4_a.c
@@ -35,14 +35,12 @@ static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,
                                      struct net_device *dev)
 {
        struct dsa_port *dp = dsa_slave_to_port(dev);
+       __be16 *p;
        u8 *tag;
-       u16 *p;
        u16 out;
 
        /* Pad out to at least 60 bytes */
-       if (unlikely(eth_skb_pad(skb)))
-               return NULL;
-       if (skb_cow_head(skb, RTL4_A_HDR_LEN) < 0)
+       if (unlikely(__skb_put_padto(skb, ETH_ZLEN, false)))
                return NULL;
 
        netdev_dbg(dev, "add realtek tag to package to port %d\n",
@@ -53,13 +51,13 @@ static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,
        tag = skb->data + 2 * ETH_ALEN;
 
        /* Set Ethertype */
-       p = (u16 *)tag;
+       p = (__be16 *)tag;
        *p = htons(RTL4_A_ETHERTYPE);
 
        out = (RTL4_A_PROTOCOL_RTL8366RB << 12) | (2 << 8);
-       /* The lower bits is the port numer */
+       /* The lower bits is the port number */
        out |= (u8)dp->index;
-       p = (u16 *)(tag + 2);
+       p = (__be16 *)(tag + 2);
        *p = htons(out);
 
        return skb;