From: Taehee Yoo <ap420073@gmail.com>
Date: Mon, 21 Oct 2019 18:47:53 +0000
Subject: bonding: use dynamic lockdep key instead of subclass
Patch-mainline: v5.4-rc6
Git-commit: 089bca2caed0d0dea7da235ce1fe245808f5ec02
References: bsc#1154353 bnc#1151927 5.3.11

All bonding device has same lockdep key and subclass is initialized with
nest_level.
But actual nest_level value can be changed when a lower device is attached.
And at this moment, the subclass should be updated but it seems to be
unsafe.
So this patch makes bonding use dynamic lockdep key instead of the
subclass.

Test commands:
    ip link add bond0 type bond

    for i in {1..5}
    do
	    let A=$i-1
	    ip link add bond$i type bond
	    ip link set bond$i master bond$A
    done
    ip link set bond5 master bond0

Splat looks like:
[  307.992912] WARNING: possible recursive locking detected
[  307.993656] 5.4.0-rc3+ #96 Tainted: G        W
[  307.994367] --------------------------------------------
[  307.995092] ip/761 is trying to acquire lock:
[  307.995710] ffff8880513aac60 (&(&bond->stats_lock)->rlock#2/2){+.+.}, at: bond_get_stats+0xb8/0x500 [bonding]
[  307.997045]
	       but task is already holding lock:
[  307.997923] ffff88805fcbac60 (&(&bond->stats_lock)->rlock#2/2){+.+.}, at: bond_get_stats+0xb8/0x500 [bonding]
[  307.999215]
	       other info that might help us debug this:
[  308.000251]  Possible unsafe locking scenario:

[  308.001137]        CPU0
[  308.001533]        ----
[  308.001915]   lock(&(&bond->stats_lock)->rlock#2/2);
[  308.002609]   lock(&(&bond->stats_lock)->rlock#2/2);
[  308.003302]
		*** DEADLOCK ***

[  308.004310]  May be due to missing lock nesting notation

[  308.005319] 3 locks held by ip/761:
[  308.005830]  #0: ffffffff9fcc42b0 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x466/0x8a0
[  308.006894]  #1: ffff88805fcbac60 (&(&bond->stats_lock)->rlock#2/2){+.+.}, at: bond_get_stats+0xb8/0x500 [bonding]
[  308.008243]  #2: ffffffff9f9219c0 (rcu_read_lock){....}, at: bond_get_stats+0x9f/0x500 [bonding]
[  308.009422]
	       stack backtrace:
[  308.010124] CPU: 0 PID: 761 Comm: ip Tainted: G        W         5.4.0-rc3+ #96
[  308.011097] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[  308.012179] Call Trace:
[  308.012601]  dump_stack+0x7c/0xbb
[  308.013089]  __lock_acquire+0x269d/0x3de0
[  308.013669]  ? register_lock_class+0x14d0/0x14d0
[  308.014318]  lock_acquire+0x164/0x3b0
[  308.014858]  ? bond_get_stats+0xb8/0x500 [bonding]
[  308.015520]  _raw_spin_lock_nested+0x2e/0x60
[  308.016129]  ? bond_get_stats+0xb8/0x500 [bonding]
[  308.017215]  bond_get_stats+0xb8/0x500 [bonding]
[  308.018454]  ? bond_arp_rcv+0xf10/0xf10 [bonding]
[  308.019710]  ? rcu_read_lock_held+0x90/0xa0
[  308.020605]  ? rcu_read_lock_sched_held+0xc0/0xc0
[  308.021286]  ? bond_get_stats+0x9f/0x500 [bonding]
[  308.021953]  dev_get_stats+0x1ec/0x270
[  308.022508]  bond_get_stats+0x1d1/0x500 [bonding]

Fixes: d3fff6c443fe ("net: add netdev_lockdep_set_classes() helper")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/bonding/bond_main.c |   10 +++++++---
 include/net/bonding.h           |    1 +
 2 files changed, 8 insertions(+), 3 deletions(-)

--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3459,7 +3459,7 @@ static void bond_get_stats(struct net_de
 	struct list_head *iter;
 	struct slave *slave;
 
-	spin_lock_nested(&bond->stats_lock, bond_get_nest_level(bond_dev));
+	spin_lock(&bond->stats_lock);
 	memcpy(stats, &bond->bond_stats, sizeof(*stats));
 
 	rcu_read_lock();
@@ -4297,8 +4297,6 @@ void bond_setup(struct net_device *bond_
 {
 	struct bonding *bond = netdev_priv(bond_dev);
 
-	spin_lock_init(&bond->mode_lock);
-	spin_lock_init(&bond->stats_lock);
 	bond->params = bonding_defaults;
 
 	/* Initialize pointers */
@@ -4367,6 +4365,7 @@ static void bond_uninit(struct net_devic
 
 	list_del(&bond->bond_list);
 
+	lockdep_unregister_key(&bond->stats_lock_key);
 	bond_debug_unregister(bond);
 }
 
@@ -4772,6 +4771,11 @@ static int bond_init(struct net_device *
 
 	bond->nest_level = SINGLE_DEPTH_NESTING;
 
+	spin_lock_init(&bond->mode_lock);
+	spin_lock_init(&bond->stats_lock);
+	lockdep_register_key(&bond->stats_lock_key);
+	lockdep_set_class(&bond->stats_lock, &bond->stats_lock_key);
+
 	list_add_tail(&bond->bond_list, &bn->dev_list);
 
 	bond_prepare_sysfs_group(bond);
--- a/include/net/bonding.h
+++ b/include/net/bonding.h
@@ -239,6 +239,7 @@ struct bonding {
 	struct	 dentry *debug_dir;
 #endif /* CONFIG_DEBUG_FS */
 	struct rtnl_link_stats64 bond_stats;
+	struct lock_class_key stats_lock_key;
 };
 
 #define bond_slave_get_rcu(dev) \