[IPV4]: Fix rtm_to_ifaddr() error handling.

Return negative error value (embedded in the pointer) instead of
returning NULL.

Signed-off-by: Evgeniy Polyakov <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/devinet.c

···
 		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) {