From 6afcb89b4438ef6fa8f969f95eaf105b611a346c Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Mon, 15 Oct 2007 01:47:15 -0700
Subject: [PATCH] --- yaml --- r: 69412 b: refs/heads/master c:
 a030847e9f0eed2a080f6114381c649a7aa43d25 h: refs/heads/master v: v3

---
 [refs]               |  2 +-
 trunk/net/core/dev.c | 21 ++++++++++-----------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/[refs] b/[refs]
index 6d3a0900b0da..0c5c55804b25 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 172a863f2bfbacf4b6bfc06db219b946a058ce1a
+refs/heads/master: a030847e9f0eed2a080f6114381c649a7aa43d25
diff --git a/trunk/net/core/dev.c b/trunk/net/core/dev.c
index 39aba4862f21..38b03da5c1ca 100644
--- a/trunk/net/core/dev.c
+++ b/trunk/net/core/dev.c
@@ -1362,22 +1362,21 @@ int skb_checksum_help(struct sk_buff *skb)
 		goto out_set_summed;
 	}
 
-	if (skb_cloned(skb)) {
+	offset = skb->csum_start - skb_headroom(skb);
+	BUG_ON(offset >= skb_headlen(skb));
+	csum = skb_checksum(skb, offset, skb->len - offset, 0);
+
+	offset += skb->csum_offset;
+	BUG_ON(offset + sizeof(__sum16) > skb_headlen(skb));
+
+	if (skb_cloned(skb) &&
+	    !skb_clone_writable(skb, offset + sizeof(__sum16))) {
 		ret = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
 		if (ret)
 			goto out;
 	}
 
-	offset = skb->csum_start - skb_headroom(skb);
-	BUG_ON(offset > (int)skb->len);
-	csum = skb_checksum(skb, offset, skb->len-offset, 0);
-
-	offset = skb_headlen(skb) - offset;
-	BUG_ON(offset <= 0);
-	BUG_ON(skb->csum_offset + 2 > offset);
-
-	*(__sum16 *)(skb->head + skb->csum_start + skb->csum_offset) =
-		csum_fold(csum);
+	*(__sum16 *)(skb->data + offset) = csum_fold(csum);
 out_set_summed:
 	skb->ip_summed = CHECKSUM_NONE;
 out: