netdev - Memory leaks in IPv6 ndisc on v4.19.56

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Message-ID: <8fadeb22-2a9b-6038-01f9-bf32b5055965@linuxlounge.net>
Date:   Tue, 2 Jul 2019 15:05:36 +0200
From:   Martin Weinelt <martin@...uxlounge.net>
To:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        netdev@...r.kernel.org
Subject: Memory leaks in IPv6 ndisc on v4.19.56

Hi everyone,

I've been experiencing memory leaks on the v4.19 series. I've started
seeing them on Debian with v4.19.16 and I can reproduce them on v4.19.56
using Debians kernel config. I was unable to reproduce this on 
v5.2.0-rc6/rc7.

  [ 1899.380321] kmemleak: 1138 new suspected memory leaks (see /sys/kernel/debug/kmemleak)

On the machines in question we're running routers for a mesh networking
setup based on the batman-adv kmod. Our setup consists of KVM guests 
running Debian, with each router having 18 bridges with the following
master/slave relationship:

  bridge -> batman-adv -> {L2 tunnel, virtio net device}

I've attached the output of kmemleak and I've looked up the top-most
function offsets below:

Best,
  Martin


$ ./faddr2line /usr/lib/debug/lib/modules/4.19.56/vmlinux ndisc_recv_ns+0x356/0x5f0
ndisc_recv_ns+0x356/0x5f0:
__neigh_lookup at include/net/neighbour.h:513
(inlined by) ndisc_recv_ns at net/ipv6/ndisc.c:916

$ ./faddr2line /usr/lib/debug/lib/modules/4.19.56/vmlinux ndisc_router_discovery+0x4ab/0xae0
ndisc_router_discovery+0x4ab/0xae0:
__neigh_lookup at include/net/neighbour.h:513
(inlined by) ndisc_router_discovery at net/ipv6/ndisc.c:1387

$ ./faddr2line /usr/lib/debug/lib/modules/4.19.56/vmlinux ndisc_recv_rs+0x173/0x1b0
ndisc_recv_rs+0x173/0x1b0:
ndisc_recv_rs at net/ipv6/ndisc.c:1095

$ ./faddr2line /usr/lib/debug/lib/modules/4.19.56/vmlinux ip6_finish_output2+0x211/0x570
ip6_finish_output2+0x211/0x570:
ip6_finish_output2 at net/ipv6/ip6_output.c:117


View attachment "kmemleak.log" of type "text/x-log" (179770 bytes)