On 2024/5/6 13:51, Ratheesh Kannoth wrote:
On 2024-05-06 at 07:24:39, Wen Gu (guwen@xxxxxxxxxxxxxxxxx) wrote:A netdev refcnt leak issue was found when unregistering netdev after using SMC. It can be reproduced as follows. - run tests based on SMC. - unregister the net device. The following error message can be observed. 'unregister_netdevice: waiting for ethx to become free. Usage count = x' With CONFIG_NET_DEV_REFCNT_TRACKER set, more detailed error message can be provided by refcount tracker: unregister_netdevice: waiting for eth1 to become free. Usage count = 2 ref_tracker: eth%d@ffff9cabc3bf8548 has 1/1 users at ___neigh_create+0x8e/0x420 neigh_event_ns+0x52/0xc0 arp_process+0x7c0/0x860 __netif_receive_skb_list_core+0x258/0x2c0 __netif_receive_skb_list+0xea/0x150 netif_receive_skb_list_internal+0xf2/0x1b0 napi_complete_done+0x73/0x1b0 mlx5e_napi_poll+0x161/0x5e0 [mlx5_core] __napi_poll+0x2c/0x1c0 net_rx_action+0x2a7/0x380 __do_softirq+0xcd/0x2a7 It is because in smc_ib_find_route(), neigh_lookup() takes a netdev refcnt but does not release. So fix it. Fixes: e5c4744cfb59 ("net/smc: add SMC-Rv2 connection establishment") Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx> --- net/smc/smc_ib.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c index 97704a9e84c7..b431bd8a5172 100644 --- a/net/smc/smc_ib.c +++ b/net/smc/smc_ib.c @@ -210,10 +210,11 @@ int smc_ib_find_route(struct net *net, __be32 saddr, __be32 daddr, goto out; if (rt->rt_uses_gateway && rt->rt_gw_family != AF_INET)need to release it here as well ?
Do you mean call ip_rt_put() to release rt? Yes, after investigating here, I agree that rt needs to be released as well. Thanks!
goto out; - neigh = rt->dst.ops->neigh_lookup(&rt->dst, NULL, &fl4.daddr); + neigh = dst_neigh_lookup(&rt->dst, &fl4.daddr); if (neigh) { memcpy(nexthop_mac, neigh->ha, ETH_ALEN); *uses_gateway = rt->rt_uses_gateway; + neigh_release(neigh); return 0; } out: -- 2.32.0.3.g01195cf9f
