ipv6: addrconf_f6i_alloc - fix non-null pointer check to !IS_ERR()

Fixes a stupid bug I recently introduced...
ip6_route_info_create() returns an ERR_PTR(err) and not a NULL on error.

Fixes: d55a2e3 ("net-ipv6: fix excessive RTF_ADDRCONF flag on ::1/128 local route (and others)'")
Cc: David Ahern <[email protected]>
Cc: Lorenzo Colitti <[email protected]>
Cc: Eric Dumazet <[email protected]>
Signed-off-by: Maciej Żenczykowski <[email protected]>
Reported-by: syzbot <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: zenczykowski

net/ipv6/route.c

@@ -4406,7 +4406,7 @@ struct fib6_info *addrconf_f6i_alloc(struct net *net,
 	}
 
 	f6i = ip6_route_info_create(&cfg, gfp_flags, NULL);
-	if (f6i)
+	if (!IS_ERR(f6i))
 		f6i->dst_nocount = true;
 	return f6i;
 }