From 992cba7e276d438ac8b0a8c17b147b37c8c286f7 Mon Sep 17 00:00:00 2001
From: "David S. Miller" <davem@davemloft.net>
Date: Tue, 31 Jul 2018 15:27:56 -0700
Subject: [PATCH] net: Add and use skb_list_del_init().

It documents what is happening, and eliminates the spurious list
pointer poisoning.

In the long term, in order to get proper list head debugging, we
might want to use the list poison value as the indicator that
an SKB is a singleton and not on a list.

Signed-off-by: David S. Miller <davem@davemloft.net>
---
 include/linux/skbuff.h | 6 ++++++
 net/core/dev.c         | 6 ++----
 net/ipv4/ip_input.c    | 6 +-----
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c4c9e3f5cd9ac2..e3a53ca4a9b51b 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1344,6 +1344,12 @@ static inline void skb_mark_not_on_list(struct sk_buff *skb)
 	skb->next = NULL;
 }
 
+static inline void skb_list_del_init(struct sk_buff *skb)
+{
+	__list_del_entry(&skb->list);
+	skb_mark_not_on_list(skb);
+}
+
 /**
  *	skb_queue_empty - check if a queue is empty
  *	@list: queue head
diff --git a/net/core/dev.c b/net/core/dev.c
index f76dd7e14dd616..0b2d777e5b9e85 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5295,8 +5295,7 @@ static void __napi_gro_flush_chain(struct napi_struct *napi, u32 index,
 	list_for_each_entry_safe_reverse(skb, p, head, list) {
 		if (flush_old && NAPI_GRO_CB(skb)->age == jiffies)
 			return;
-		list_del(&skb->list);
-		skb_mark_not_on_list(skb);
+		skb_list_del_init(skb);
 		napi_gro_complete(skb);
 		napi->gro_hash[index].count--;
 	}
@@ -5481,8 +5480,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
 	ret = NAPI_GRO_CB(skb)->free ? GRO_MERGED_FREE : GRO_MERGED;
 
 	if (pp) {
-		list_del(&pp->list);
-		skb_mark_not_on_list(pp);
+		skb_list_del_init(pp);
 		napi_gro_complete(pp);
 		napi->gro_hash[hash].count--;
 	}
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index eba7f3883230a0..35a786c0aaa064 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -531,11 +531,7 @@ static void ip_sublist_rcv_finish(struct list_head *head)
 	struct sk_buff *skb, *next;
 
 	list_for_each_entry_safe(skb, next, head, list) {
-		list_del(&skb->list);
-		/* Handle ip{6}_forward case, as sch_direct_xmit have
-		 * another kind of SKB-list usage (see validate_xmit_skb_list)
-		 */
-		skb_mark_not_on_list(skb);
+		skb_list_del_init(skb);
 		dst_input(skb);
 	}
 }