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netfilter: nfnetlink: fix splat due to incorrect socket memory accoun…
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…ting in skbuff clones

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+ torvalds#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 633c9a8 ("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@gmail.com>
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Tested-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
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@ummakynes @umakrishn
ummakynes authored and umakrishn committed Jan 12, 2016
1 parent 6bd6a17 commit 8f5dcac
Showing 1 changed file with 0 additions and 2 deletions.
2 changes: 0 additions & 2 deletions net/netfilter/nfnetlink.c
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Original file line number Diff line number Diff line change
Expand Up @@ -295,8 +295,6 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
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));
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