netdev - [PATCH 6/7] [PPP] generic: Call skb_cow

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Message-Id: <E1IR2XP-0007QP-00@gondolin.me.apana.org.au>
Date:	Fri, 31 Aug 2007 17:11:35 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	James Chapman <jchapman@...alix.com>,
	"David S. Miller" <davem@...emloft.net>,
	Michal Ostrowski <mostrows@...akeasy.net>,
	Paul Mackerras <paulus@...ba.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Toralf F?rster <toralf.foerster@....de>, netdev@...r.kernel.org
Subject: [PATCH 6/7] [PPP] generic: Call skb_cow_head before scribbling over skb

[PPP] generic: Call skb_cow_head before scribbling over skb

It's rude to write over data that other people are still using.  So call
skb_cow_head before PPP proceeds to modify the skb data.

Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
---

 drivers/net/ppp_generic.c |   14 +++-----------
 1 files changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 9293c82..7e21342 100644
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -899,17 +899,9 @@ ppp_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	/* Put the 2-byte PPP protocol number on the front,
 	   making sure there is room for the address and control fields. */
-	if (skb_headroom(skb) < PPP_HDRLEN) {
-		struct sk_buff *ns;
-
-		ns = alloc_skb(skb->len + dev->hard_header_len, GFP_ATOMIC);
-		if (ns == 0)
-			goto outf;
-		skb_reserve(ns, dev->hard_header_len);
-		skb_copy_bits(skb, 0, skb_put(ns, skb->len), skb->len);
-		kfree_skb(skb);
-		skb = ns;
-	}
+	if (skb_cow_head(skb, PPP_HDRLEN))
+		goto outf;
+
 	pp = skb_push(skb, 2);
 	proto = npindex_to_proto[npi];
 	pp[0] = proto >> 8;
-
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