ipv6: prevent speculative execution

CVE-2017-5753
CVE-2017-5715

Real commit text tbd
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
(cherry picked from commit 2b6906d0cf28910144b1e1816861097b2ae3d4a1)
Signed-off-by: Andy Whitcroft <apw@canonical.com>

net/ipv6/raw.c

@@ -717,6 +717,7 @@ static int raw6_getfrag(void *from, char *to, int offset, int len, int odd,
 	if (offset < rfv->hlen) {
 		int copy = min(rfv->hlen - offset, len);
 
+		gmb();
 		if (skb->ip_summed == CHECKSUM_PARTIAL)
 			memcpy(to, rfv->c + offset, copy);
 		else