openwrtv3/target/linux/generic/patches-4.4/030-1-smsc95xx-Use-skb_cow_head-to-deal-with-cloned-skbs.patch
Álvaro Fernández Rojas 2db05cd199 kernel: use skb_cow_head() to deal with cloned skbs
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 Ethernet<->WiFi bridge for Raspberry Pi and probably other devices.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
2017-04-23 13:51:55 +02:00

40 lines
1.4 KiB
Diff

From e9156cd26a495a18706e796f02a81fee41ec14f4 Mon Sep 17 00:00:00 2001
From: James Hughes <james.hughes@raspberrypi.org>
Date: Wed, 19 Apr 2017 11:13:40 +0100
Subject: [PATCH] smsc95xx: Use skb_cow_head to deal with cloned skbs
The driver was failing to check that the SKB wasn't cloned
before adding checksum data.
Replace existing handling to extend/copy the header buffer
with skb_cow_head.
Signed-off-by: James Hughes <james.hughes@raspberrypi.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Woojung Huh <Woojung.Huh@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
drivers/net/usb/smsc95xx.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1835,13 +1835,13 @@ static struct sk_buff *smsc95xx_tx_fixup
/* We do not advertise SG, so skbs should be already linearized */
BUG_ON(skb_shinfo(skb)->nr_frags);
- if (skb_headroom(skb) < overhead) {
- struct sk_buff *skb2 = skb_copy_expand(skb,
- overhead, 0, flags);
+ /* Make writable and expand header space by overhead if required */
+ if (skb_cow_head(skb, overhead)) {
+ /* Must deallocate here as returning NULL to indicate error
+ * means the skb won't be deallocated in the caller.
+ */
dev_kfree_skb_any(skb);
- skb = skb2;
- if (!skb)
- return NULL;
+ return NULL;
}
if (csum) {