drivers/net/wan/hdlc_fr: Fix a double free in pvc_xmit

[ Upstream commit 1b479fb ]

In pvc_xmit, if __skb_pad(skb, pad, false) failed, it will free
the skb in the first time and goto drop. But the same skb is freed
by kfree_skb(skb) in the second time in drop.

Maintaining the original function unchanged, my patch adds a new
label out to avoid the double free if __skb_pad() failed.

Fixes: f5083d0 ("drivers/net/wan/hdlc_fr: Improvements to the code of pvc_xmit")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/wan/hdlc_fr.c

@@ -415,7 +415,7 @@ static netdev_tx_t pvc_xmit(struct sk_buff *skb, struct net_device *dev)
 
 		if (pad > 0) { /* Pad the frame with zeros */
 			if (__skb_pad(skb, pad, false))
-				goto drop;
+				goto out;
 			skb_put(skb, pad);
 		}
 	}
@@ -448,8 +448,9 @@ static netdev_tx_t pvc_xmit(struct sk_buff *skb, struct net_device *dev)
 	return NETDEV_TX_OK;
 
 drop:
-	dev->stats.tx_dropped++;
 	kfree_skb(skb);
+out:
+	dev->stats.tx_dropped++;
 	return NETDEV_TX_OK;
 }