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bonding: use dynamic lockdep key instead of subclass
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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: d3fff6c ("net: add netdev_lockdep_set_classes() helper")
Signed-off-by: Taehee Yoo <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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TaeheeYoo authored and davem330 committed Oct 24, 2019
1 parent 65de65d commit 089bca2
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Showing 2 changed files with 8 additions and 3 deletions.
10 changes: 7 additions & 3 deletions drivers/net/bonding/bond_main.c
Original file line number Diff line number Diff line change
Expand Up @@ -3459,7 +3459,7 @@ static void bond_get_stats(struct net_device *bond_dev,
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();
Expand Down Expand Up @@ -4297,8 +4297,6 @@ void bond_setup(struct net_device *bond_dev)
{
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 */
Expand Down Expand Up @@ -4367,6 +4365,7 @@ static void bond_uninit(struct net_device *bond_dev)

list_del(&bond->bond_list);

lockdep_unregister_key(&bond->stats_lock_key);
bond_debug_unregister(bond);
}

Expand Down Expand Up @@ -4772,6 +4771,11 @@ static int bond_init(struct net_device *bond_dev)

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);
Expand Down
1 change: 1 addition & 0 deletions include/net/bonding.h
Original file line number Diff line number Diff line change
Expand Up @@ -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) \
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