net: add kfree_skb_list()

Extracted from upstream commit bd8a7036 "gre: fix a possible skb leak".

This patch adds a kfree_skb_list() helper.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

include/linux/skbuff.h

@@ -534,6 +534,7 @@ static inline struct rtable *skb_rtable(const struct sk_buff *skb)
 }
 
 extern void kfree_skb(struct sk_buff *skb);
+extern void kfree_skb_list(struct sk_buff *segs);
 extern void consume_skb(struct sk_buff *skb);
 extern void	       __kfree_skb(struct sk_buff *skb);
 extern struct sk_buff *__alloc_skb(unsigned int size,

net/core/skbuff.c

@@ -277,15 +277,8 @@ EXPORT_SYMBOL(dev_alloc_skb);
 
 static void skb_drop_list(struct sk_buff **listp)
 {
-	struct sk_buff *list = *listp;
-
+	kfree_skb_list(*listp);
 	*listp = NULL;
-
-	do {
-		struct sk_buff *this = list;
-		list = list->next;
-		kfree_skb(this);
-	} while (list);
 }
 
 static inline void skb_drop_fraglist(struct sk_buff *skb)
@@ -436,6 +429,17 @@ void kfree_skb(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(kfree_skb);
 
+void kfree_skb_list(struct sk_buff *segs)
+{
+	while (segs) {
+		struct sk_buff *next = segs->next;
+
+		kfree_skb(segs);
+		segs = next;
+	}
+}
+EXPORT_SYMBOL(kfree_skb_list);
+
 /**
  *	consume_skb - free an skbuff
  *	@skb: buffer to free