netdev - Re: Memory leaks in conntrack

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Date:   Wed, 13 Sep 2017 10:58:37 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Florian Westphal <fw@...len.de>
Cc:     netfilter-devel@...r.kernel.org,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: Memory leaks in conntrack

On Wed, Sep 13, 2017 at 9:45 AM, Cong Wang <xiyou.wangcong@...il.com> wrote:
> On Wed, Sep 13, 2017 at 1:05 AM, Florian Westphal <fw@...len.de> wrote:
>> Cong Wang <xiyou.wangcong@...il.com> wrote:
>>> While testing my TC filter patches (so not related to conntrack), the
>>> following memory leaks are shown up:
>>>
>>> unreferenced object 0xffff9b19ba551228 (size 128):
>>>   comm "chronyd", pid 338, jiffies 4294910829 (age 53.188s)
>>>   hex dump (first 32 bytes):
>>>     6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
>>>     00 00 00 00 18 00 00 30 00 00 00 00 00 00 00 00  .......0........
>>>   backtrace:
>>>     [<ffffffff9f1e1175>] create_object+0x169/0x2aa
>>>     [<ffffffff9fb77fb2>] kmemleak_alloc+0x25/0x41
>>>     [<ffffffff9f1c47ed>] slab_post_alloc_hook+0x44/0x65
>>>     [<ffffffff9f1ca2db>] __kmalloc_track_caller+0x113/0x146
>>>     [<ffffffff9f193c3b>] __krealloc+0x4a/0x69
>>>     [<ffffffff9f948dbd>] nf_ct_ext_add+0xe1/0x145
>>>     [<ffffffff9f942395>] init_conntrack+0x1f7/0x36e
>>>     [<ffffffff9f942762>] nf_conntrack_in+0x1d3/0x326
>>>     [<ffffffff9fa1ea69>] ipv4_conntrack_local+0x4d/0x50
>>>     [<ffffffff9f93ad70>] nf_hook_slow+0x3c/0x9b
>>>     [<ffffffff9f9c7999>] nf_hook.constprop.40+0xbe/0xd8
>>>     [<ffffffff9f9c7ba2>] __ip_local_out+0xb3/0xbf
>>>     [<ffffffff9f9c7bca>] ip_local_out+0x1c/0x36
>>>     [<ffffffff9f9c9216>] ip_send_skb+0x19/0x3d
>>>     [<ffffffff9f9ee3de>] udp_send_skb+0x17e/0x1df
>>>     [<ffffffff9f9eea37>] udp_sendmsg+0x5a2/0x77c
>>> unreferenced object 0xffff9b19a69b3340 (size 336):
>>>   comm "chronyd", pid 338, jiffies 4294910868 (age 53.032s)
>>>   hex dump (first 32 bytes):
>>>     01 00 00 00 5a 5a 5a 5a 00 00 00 00 ad 4e ad de  ....ZZZZ.....N..
>>>     ff ff ff ff 5a 5a 5a 5a ff ff ff ff ff ff ff ff  ....ZZZZ........
>>>   backtrace:
>>>     [<ffffffff9f1e1175>] create_object+0x169/0x2aa
>>>     [<ffffffff9fb77fb2>] kmemleak_alloc+0x25/0x41
>>>     [<ffffffff9f1c47ed>] slab_post_alloc_hook+0x44/0x65
>>>     [<ffffffff9f1c7a7d>] kmem_cache_alloc+0xd7/0x1f1
>>>     [<ffffffff9f941b78>] __nf_conntrack_alloc+0xa2/0x146
>>>     [<ffffffff9f942250>] init_conntrack+0xb2/0x36e
>>>     [<ffffffff9f942762>] nf_conntrack_in+0x1d3/0x326
>>>     [<ffffffff9fa1ea69>] ipv4_conntrack_local+0x4d/0x50
>>>     [<ffffffff9f93ad70>] nf_hook_slow+0x3c/0x9b
>>>     [<ffffffff9f9c7999>] nf_hook.constprop.40+0xbe/0xd8
>>>     [<ffffffff9f9c7ba2>] __ip_local_out+0xb3/0xbf
>>>     [<ffffffff9f9c7bca>] ip_local_out+0x1c/0x36
>>>     [<ffffffff9f9c9216>] ip_send_skb+0x19/0x3d
>>>     [<ffffffff9f9ee3de>] udp_send_skb+0x17e/0x1df
>>>     [<ffffffff9f9eea37>] udp_sendmsg+0x5a2/0x77c
>>>     [<ffffffff9f9f8cb8>] inet_sendmsg+0x37/0x5e
>>>
>>> I don't touch chronyd in my VM, so I have no idea why it sends out UDP
>>> packets, my guess is it is some periodical packet.
>>>
>>> I don't think I use conntrack either, since /proc/net/ip_conntrack
>>> does not exist.
>>
>> You probably do, can you try "cat /proc/net/nf_conntrack" instead?
>>
>> (otherwise there should be no ipv4_conntrack_local() invocation
>>  since we would not register this hook at all).
>
> Yeah it is very weird but it is true:
>
> [root@...alhost ~]# echo scan > /sys/kernel/debug/kmemleak
> [  133.450823] kmemleak: 18 new suspected memory leaks (see
> /sys/kernel/debug/kmemleak)
> [root@...alhost ~]# cat /proc/net/ip_conntrack
> cat: /proc/net/ip_conntrack: No such file or directory
> [root@...alhost ~]# cat /sys/kernel/debug/kmemleak
> unreferenced object 0xffff95c1e0b24040 (size 336):
> ...

Oops, you mean nf_conntrack... Here we go:

[root@...alhost ~]# cat /proc/net/nf_conntrack
ipv4     2 udp      17 116 src=192.168.124.6 dst=204.2.134.162
sport=123 dport=123 src=204.2.134.162 dst=192.168.124.6 sport=123
dport=123 [ASSURED] mark=0 zone=0 use=2
ipv4     2 udp      17 117 src=192.168.124.6 dst=45.79.187.10
sport=123 dport=123 src=45.79.187.10 dst=192.168.124.6 sport=123
dport=123 [ASSURED] mark=0 zone=0 use=2
ipv4     2 udp      17 110 src=192.168.124.6 dst=192.168.124.1
sport=35486 dport=53 src=192.168.124.1 dst=192.168.124.6 sport=53
dport=35486 [ASSURED] mark=0 zone=0 use=2
ipv4     2 udp      17 110 src=192.168.124.6 dst=192.168.124.1
sport=52373 dport=53 src=192.168.124.1 dst=192.168.124.6 sport=53
dport=52373 [ASSURED] mark=0 zone=0 use=2
ipv4     2 unknown  2 518 src=192.168.124.6 dst=224.0.0.22 [UNREPLIED]
src=224.0.0.22 dst=192.168.124.6 mark=0 zone=0 use=2
ipv4     2 udp      17 110 src=192.168.124.6 dst=192.168.124.1
sport=43242 dport=53 src=192.168.124.1 dst=192.168.124.6 sport=53
dport=43242 [ASSURED] mark=0 zone=0 use=2
ipv4     2 udp      17 116 src=192.168.124.6 dst=96.226.123.196
sport=123 dport=123 src=96.226.123.196 dst=192.168.124.6 sport=123
dport=123 [ASSURED] mark=0 zone=0 use=2
ipv4     2 udp      17 110 src=192.168.124.6 dst=192.168.124.1
sport=42838 dport=53 src=192.168.124.1 dst=192.168.124.6 sport=53
dport=42838 [ASSURED] mark=0 zone=0 use=2
ipv4     2 udp      17 117 src=192.168.124.6 dst=97.127.104.4
sport=123 dport=123 src=97.127.104.4 dst=192.168.124.6 sport=123
dport=123 [ASSURED] mark=0 zone=0 use=2