[IPV4]: Fix rtm_to_ifaddr() error handling.

Return negative error value (embedded in the pointer) instead of
returning NULL.
Signed-off-by: NEvgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/devinet.c

@@ -502,8 +502,10 @@ static struct in_ifaddr *rtm_to_ifaddr(struct nlmsghdr *nlh)
 		goto errout;
 
 	ifm = nlmsg_data(nlh);
-	if (ifm->ifa_prefixlen > 32 || tb[IFA_LOCAL] == NULL)
+	if (ifm->ifa_prefixlen > 32 || tb[IFA_LOCAL] == NULL) {
+		err = -EINVAL;
 		goto errout;
+	}
 
 	dev = __dev_get_by_index(ifm->ifa_index);
 	if (dev == NULL) {