linux-kernel - [PATCH 3.16 164/178] sr9700: use skb_cow

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Message-ID: <lsq.1500213406.110036893@decadent.org.uk>
Date:   Sun, 16 Jul 2017 14:56:46 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Eric Dumazet" <edumazet@...gle.com>,
        "James Hughes" <james.hughes@...pberrypi.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.16 164/178] sr9700: use skb_cow_head() to deal with
 cloned skbs

3.16.46-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

commit d532c1082f68176363ed766d09bf187616e282fe upstream.

We need to ensure there is enough headroom to push extra header,
but we also need to check if we are allowed to change headers.

skb_cow_head() is the proper helper to deal with this.

Fixes: c9b37458e956 ("USB2NET : SR9700 : One chip USB 1.1 USB2NET SR9700Device Driver Support")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: James Hughes <james.hughes@...pberrypi.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/usb/sr9700.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

--- a/drivers/net/usb/sr9700.c
+++ b/drivers/net/usb/sr9700.c
@@ -456,14 +456,9 @@ static struct sk_buff *sr9700_tx_fixup(s
 
 	len = skb->len;
 
-	if (skb_headroom(skb) < SR_TX_OVERHEAD) {
-		struct sk_buff *skb2;
-
-		skb2 = skb_copy_expand(skb, SR_TX_OVERHEAD, 0, flags);
+	if (skb_cow_head(skb, SR_TX_OVERHEAD)) {
 		dev_kfree_skb_any(skb);
-		skb = skb2;
-		if (!skb)
-			return NULL;
+		return NULL;
 	}
 
 	__skb_push(skb, SR_TX_OVERHEAD);