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[PATCH 1/1 linux-next] netfilter: conntrack: fix kmemleak false positive

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Since commit f330a7fdbe16
("netfilter: conntrack: get rid of conntrack timer")

closed connections remain longer in /proc/net/nf_conntrack

Running current kernel; just after boot:
cat /proc/net/nf_conntrack | wc -l = 5
4 minutes required to clean up the table.

Going back to kernel version before commit above there are
no connections after some seconds.

Referring to the commit changelog this was an expected behaviour but
it results in temporary kmemleak reports:

unreferenced object 0xffff88003b0e6600 (size 248):
  comm "rsyslogd", pid 1595, jiffies 4294741312 (age 7.343s)
  ...
  backtrace:
    [<ffffffff818f0163>] kmemleak_alloc+0x23/0x40
    [<ffffffff8117abf9>] kmem_cache_alloc+0xd9/0x180
    [<ffffffff817533a8>] __nf_conntrack_alloc.isra.50+0x48/0x170
    [<ffffffff81754262>] nf_conntrack_in+0x3a2/0x5f0
    [<ffffffff817bc9e0>] ipv4_conntrack_local+0x40/0x50
    [<ffffffff8174f17d>] nf_iterate+0x5d/0x70
    [<ffffffff8174f1ef>] nf_hook_slow+0x5f/0xb0
    [<ffffffff8176ffbd>] __ip_local_out+0xad/0xe0
    [<ffffffff81770007>] ip_local_out+0x17/0x40
    [<ffffffff817711f4>] ip_send_skb+0x14/0x40
    [<ffffffff81797591>] udp_send_skb+0x91/0x260
    [<ffffffff817985e5>] udp_sendmsg+0x2f5/0x950
    [<ffffffff817a4f80>] inet_sendmsg+0x60/0x90
    [<ffffffff816fe7d3>] sock_sendmsg+0x33/0x40
    [<ffffffff816fed0e>] SYSC_sendto+0xee/0x160
    [<ffffffff816ff719>] SyS_sendto+0x9/0x10

(248 bytes being an nf_conn structure)

Those structures being cleared in gc_worker() later on we can't talk
about unreferenced object so this patch uses kmemleak_not_leak() to
prevent those warnings.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
---
 net/netfilter/nf_conntrack_core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 50106a1..59396f3 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1022,6 +1022,7 @@ __nf_conntrack_alloc(struct net *net,
 	 * SLAB_DESTROY_BY_RCU.
 	 */
 	ct = kmem_cache_alloc(nf_conntrack_cachep, gfp);
+	kmemleak_not_leak(ct);
 	if (ct == NULL)
 		goto out;
 
-- 
2.8.1

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[PATCH 1/1 linux-next] netfilter: conntrack: fix kmemleak false positive Fabian Frederick <fabf@skynet.be> - 2016-09-21 22:00 +0200
  Re: [PATCH 1/1 linux-next] netfilter: conntrack: fix kmemleak false  positive Florian Westphal <fw@strlen.de> - 2016-09-21 23:10 +0200
    Re: [PATCH 1/1 linux-next] netfilter: conntrack: fix kmemleak false  positive Fabian Frederick <fabf@skynet.be> - 2016-09-22 20:00 +0200
      Re: [PATCH 1/1 linux-next] netfilter: conntrack: fix kmemleak false  positive Florian Westphal <fw@strlen.de> - 2016-09-23 00:00 +0200

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