If we attach the sk to the skb from nfnetlink_rcv_batch(), then
netlink_skb_destructor() will underflow the socket receive memory
counter and we get warning splat when releasing the socket.
$ cat /proc/net/netlink
sk Eth Pid Groups Rmem Wmem Dump Locks Drops Inode
ffff8800ca903000 12 0 00000000 -54144 0 0 2 0 17942
^^^^^^
Rmem above shows an underflow.
And here below the warning splat:
[ 1363.815976] WARNING: CPU: 2 PID: 1356 at net/netlink/af_netlink.c:958 netlink_sock_destruct+0x80/0xb9()
[...]
[ 1363.816152] CPU: 2 PID: 1356 Comm: kworker/u16:1 Tainted: G W 4.4.0-rc1+ #153
[ 1363.816155] Hardware name: LENOVO 23259H1/23259H1, BIOS G2ET32WW (1.12 ) 05/30/2012
[ 1363.816160] Workqueue: netns cleanup_net
[ 1363.816163] 0000000000000000 ffff880119203dd0 ffffffff81240204 0000000000000000
[ 1363.816169] ffff880119203e08 ffffffff8104db4b ffffffff813d49a1 ffff8800ca771000
[ 1363.816174] ffffffff81a42b00 0000000000000000 ffff8800c0afe1e0 ffff880119203e18
[ 1363.816179] Call Trace:
[ 1363.816181] <IRQ> [<ffffffff81240204>] dump_stack+0x4e/0x79
[ 1363.816193] [<ffffffff8104db4b>] warn_slowpath_common+0x9a/0xb3
[ 1363.816197] [<ffffffff813d49a1>] ? netlink_sock_destruct+0x80/0xb9
skb->sk was only needed to lookup for the netns, however we don't need
this anymore since 633c9a840d0b ("netfilter: nfnetlink: avoid recurrent
netns lookups in call_batch") so this patch removes this manual socket
assignment to resolve this problem.
Reported-by: Arturo Borrero Gonzalez <arturo.borrero.glez@xxxxxxxxx>
Reported-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Tested-by: Arturo Borrero Gonzalez <arturo.borrero.glez@xxxxxxxxx>
---
net/netfilter/nfnetlink.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 445590f..77afe91 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -295,8 +295,6 @@ replay:
if (!skb)
return netlink_ack(oskb, nlh, -ENOMEM);
- skb->sk = oskb->sk;
-
nfnl_lock(subsys_id);
ss = rcu_dereference_protected(table[subsys_id].subsys,
lockdep_is_held(&table[subsys_id].mutex));
--
2.1.4
--
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