[SRU][Trusty] Revert "net: Fix skb csum races when peeking"

[Luis Henriques]

BugLink: https://bugs.launchpad.net/bugs/1508510

This reverts commit 2dde51aa53393a531b493e3a8194e4d467e194a3, which
was commit 89c22d8c3b278212eef6a8cc66b570bc840a6f5a upstream.

A fix is being discussed upstream as stable kernels < 3.19 are impacted.

Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/core/datagram.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 13bc7dad7990..cd54bcc8f550 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -778,8 +778,7 @@ __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
 	if (likely(!sum)) {
 		if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
 			netdev_rx_csum_fault(skb->dev);
-		if (!skb_shared(skb))
-			skb->ip_summed = CHECKSUM_UNNECESSARY;
+		skb->ip_summed = CHECKSUM_UNNECESSARY;
 	}
 	return sum;
 }