4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lorenzo Colitti <lorenzo@xxxxxxxxxx> [ Upstream commit 6503a30440962f1e1ccb8868816b4e18201218d4 ] Commit 3765d35ed8b9 ("net: ipv4: Convert inet_rtm_getroute to rcu versions of route lookup") broke "ip route get" in the presence of rules that specify iif lo. Host-originated traffic always has iif lo, because ip_route_output_key_hash and ip6_route_output_flags set the flow iif to LOOPBACK_IFINDEX. Thus, putting "iif lo" in an ip rule is a convenient way to select only originated traffic and not forwarded traffic. inet_rtm_getroute used to match these rules correctly because even though it sets the flow iif to 0, it called ip_route_output_key which overwrites iif with LOOPBACK_IFINDEX. But now that it calls ip_route_output_key_hash_rcu, the ifindex will remain 0 and not match the iif lo in the rule. As a result, "ip route get" will return ENETUNREACH. Fixes: 3765d35ed8b9 ("net: ipv4: Convert inet_rtm_getroute to rcu versions of route lookup") Tested: https://android.googlesource.com/kernel/tests/+/master/net/test/multinetwork_test.py passes again Signed-off-by: Lorenzo Colitti <lorenzo@xxxxxxxxxx> Acked-by: David Ahern <dsahern@xxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ipv4/route.c | 1 + 1 file changed, 1 insertion(+) --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2762,6 +2762,7 @@ static int inet_rtm_getroute(struct sk_b if (err == 0 && rt->dst.error) err = -rt->dst.error; } else { + fl4.flowi4_iif = LOOPBACK_IFINDEX; rt = ip_route_output_key_hash_rcu(net, &fl4, &res, skb); err = 0; if (IS_ERR(rt))