From b7c8487cb3d99509220092fe77a2464dff43f015 Mon Sep 17 00:00:00 2001 From: Robert Shearman Date: Fri, 21 Apr 2017 21:34:59 +0100 Subject: [PATCH] ipv4: Avoid caching l3mdev dst on mismatched local route David reported that doing the following: ip li add red type vrf table 10 ip link set dev eth1 vrf red ip addr add 127.0.0.1/8 dev red ip link set dev eth1 up ip li set red up ping -c1 -w1 -I red 127.0.0.1 ip li del red when either policy routing IP rules are present or the local table lookup ip rule is before the l3mdev lookup results in a hang with these messages: unregister_netdevice: waiting for red to become free. Usage count = 1 The problem is caused by caching the dst used for sending the packet out of the specified interface on a local route with a different nexthop interface. Thus the dst could stay around until the route in the table the lookup was done is deleted which may be never. Address the problem by not forcing output device to be the l3mdev in the flow's output interface if the lookup didn't use the l3mdev. This then results in the dst using the right device according to the route. Changes in v2: - make the dev_out passed in by __ip_route_output_key_hash correct instead of checking the nh dev if FLOWI_FLAG_SKIP_NH_OIF is set as suggested by David. Fixes: 5f02ce24c2696 ("net: l3mdev: Allow the l3mdev to be a loopback") Reported-by: David Ahern Suggested-by: David Ahern Signed-off-by: Robert Shearman Acked-by: David Ahern Tested-by: David Ahern Signed-off-by: David S. Miller --- net/ipv4/route.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index acd69cfe2951..d9724889ff09 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2359,7 +2359,8 @@ struct rtable *__ip_route_output_key_hash(struct net *net, struct flowi4 *fl4, } /* L3 master device is the loopback for that domain */ - dev_out = l3mdev_master_dev_rcu(dev_out) ? : net->loopback_dev; + dev_out = l3mdev_master_dev_rcu(FIB_RES_DEV(res)) ? : + net->loopback_dev; fl4->flowi4_oif = dev_out->ifindex; flags |= RTCF_LOCAL; goto make_route; -- 2.20.1