netdev - Re: [PATCH net] bonding: update nest level on unlink

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Date:   Tue, 8 Jan 2019 12:33:35 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Network Development <netdev@...r.kernel.org>
Cc:     David Miller <davem@...emloft.net>,
        Jay Vosburgh <j.vosburgh@...il.com>, vfalico@...il.com,
        Andy Gospodarek <andy@...yhouse.net>,
        Willem de Bruijn <willemb@...gle.com>,
        syzbot <syzkaller@...glegroups.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net] bonding: update nest level on unlink

On Tue, Jan 8, 2019 at 12:32 PM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> From: Willem de Bruijn <willemb@...gle.com>
>
> A network device stack with multiple layers of bonding devices can
> trigger a false positive lockdep warning. Adding lockdep nest levels
> fixes this. Update the level on both enslave and unlink, to avoid the
> following series of events ..
>
>     ip netns add test
>     ip netns exec test bash
>     ip link set dev lo addr 00:11:22:33:44:55
>     ip link set dev lo down
>
>     ip link add dev bond1 type bond
>     ip link add dev bond2 type bond
>
>     ip link set dev lo master bond1
>     ip link set dev bond1 master bond2
>
>     ip link set dev bond1 nomaster
>     ip link set dev bond2 master bond1
>
> .. from still generating a splat:
>
>     [  193.652127] ======================================================
>     [  193.658231] WARNING: possible circular locking dependency detected
>     [  193.664350] 4.20.0 #8 Not tainted
>     [  193.668310] ------------------------------------------------------
>     [  193.674417] ip/15577 is trying to acquire lock:
>     [  193.678897] 00000000a40e3b69 (&(&bond->stats_lock)->rlock#3/3){+.+.}, at: bond_get_stats+0x58/0x290
>     [  193.687851]
>                but task is already holding lock:
>     [  193.693625] 00000000807b9d9f (&(&bond->stats_lock)->rlock#2/2){+.+.}, at: bond_get_stats+0x58/0x290
>
>     [..]
>
>     [  193.851092]        lock_acquire+0xa7/0x190
>     [  193.855138]        _raw_spin_lock_nested+0x2d/0x40
>     [  193.859878]        bond_get_stats+0x58/0x290
>     [  193.864093]        dev_get_stats+0x5a/0xc0
>     [  193.868140]        bond_get_stats+0x105/0x290
>     [  193.872444]        dev_get_stats+0x5a/0xc0
>     [  193.876493]        rtnl_fill_stats+0x40/0x130
>     [  193.880797]        rtnl_fill_ifinfo+0x6c5/0xdc0
>     [  193.885271]        rtmsg_ifinfo_build_skb+0x86/0xe0
>     [  193.890091]        rtnetlink_event+0x5b/0xa0
>     [  193.894320]        raw_notifier_call_chain+0x43/0x60
>     [  193.899225]        netdev_change_features+0x50/0xa0
>     [  193.904044]        bond_compute_features.isra.46+0x1ab/0x270
>     [  193.909640]        bond_enslave+0x141d/0x15b0
>     [  193.913946]        do_set_master+0x89/0xa0
>     [  193.918016]        do_setlink+0x37c/0xda0
>     [  193.921980]        __rtnl_newlink+0x499/0x890
>     [  193.926281]        rtnl_newlink+0x48/0x70
>     [  193.930238]        rtnetlink_rcv_msg+0x171/0x4b0
>     [  193.934801]        netlink_rcv_skb+0xd1/0x110
>     [  193.939103]        rtnetlink_rcv+0x15/0x20
>     [  193.943151]        netlink_unicast+0x3b5/0x520
>     [  193.947544]        netlink_sendmsg+0x2fd/0x3f0
>     [  193.951942]        sock_sendmsg+0x38/0x50
>     [  193.955899]        ___sys_sendmsg+0x2ba/0x2d0
>     [  193.960205]        __x64_sys_sendmsg+0xad/0x100
>     [  193.964687]        do_syscall_64+0x5a/0x460
>     [  193.968823]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Fixes: 7e2556e40026 ("bonding: avoid lockdep confusion in bond_get_stats()")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> ---
>  drivers/net/bonding/bond_main.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index a9d597f28023..485462d3087f 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1963,6 +1963,9 @@ static int __bond_release_one(struct net_device *bond_dev,
>         if (!bond_has_slaves(bond)) {
>                 bond_set_carrier(bond);
>                 eth_hw_addr_random(bond_dev);
> +               bond->nest_level = SINGLE_DEPTH_NESTING;
> +       } else {
> +               bond->nest_level = dev_get_nest_level(bond_dev) + 1;
>         }
>
>         unblock_netpoll_tx();
> --
> 2.20.1.97.g81188d93c3-goog
>