From: Willem de Bruijn <willemb@google.com>
Date: Tue, 8 Jan 2019 12:32:42 -0500
Subject: bonding: update nest level on unlink
Git-commit: 001e465f09a18857443489a57e74314a3368c805
Patch-mainline: v5.0-rc3
References: git-fixes

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@googlegroups.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/bonding/bond_main.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1924,6 +1924,9 @@ static int __bond_release_one(struct net
 	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();