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TaeheeYoogregkh
TaeheeYoo
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gregkh
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bonding: fix lockdep warning in bond_get_stats()
[ Upstream commit b3e80d4 ] In the "struct bonding", there is stats_lock. This lock protects "bond_stats" in the "struct bonding". bond_stats is updated in the bond_get_stats() and this function would be executed concurrently. So, the lock is needed. Bonding interfaces would be nested. So, either stats_lock should use dynamic lockdep class key or stats_lock should be used by spin_lock_nested(). In the current code, stats_lock is using a dynamic lockdep class key. But there is no updating stats_lock_key routine So, lockdep warning will occur. Test commands: ip link add bond0 type bond ip link add bond1 type bond ip link set bond0 master bond1 ip link set bond0 nomaster ip link set bond1 master bond0 Splat looks like: [ 38.420603][ T957] 5.5.0+ torvalds#394 Not tainted [ 38.421074][ T957] ------------------------------------------------------ [ 38.421837][ T957] ip/957 is trying to acquire lock: [ 38.422399][ T957] ffff888063262cd8 (&bond->stats_lock_key#2){+.+.}, at: bond_get_stats+0x90/0x4d0 [bonding] [ 38.423528][ T957] [ 38.423528][ T957] but task is already holding lock: [ 38.424526][ T957] ffff888065fd2cd8 (&bond->stats_lock_key){+.+.}, at: bond_get_stats+0x90/0x4d0 [bonding] [ 38.426075][ T957] [ 38.426075][ T957] which lock already depends on the new lock. [ 38.426075][ T957] [ 38.428536][ T957] [ 38.428536][ T957] the existing dependency chain (in reverse order) is: [ 38.429475][ T957] [ 38.429475][ T957] -> #1 (&bond->stats_lock_key){+.+.}: [ 38.430273][ T957] _raw_spin_lock+0x30/0x70 [ 38.430812][ T957] bond_get_stats+0x90/0x4d0 [bonding] [ 38.431451][ T957] dev_get_stats+0x1ec/0x270 [ 38.432088][ T957] bond_get_stats+0x1a5/0x4d0 [bonding] [ 38.432767][ T957] dev_get_stats+0x1ec/0x270 [ 38.433322][ T957] rtnl_fill_stats+0x44/0xbe0 [ 38.433866][ T957] rtnl_fill_ifinfo+0xeb2/0x3720 [ 38.434474][ T957] rtmsg_ifinfo_build_skb+0xca/0x170 [ 38.435081][ T957] rtmsg_ifinfo_event.part.33+0x1b/0xb0 [ 38.436848][ T957] rtnetlink_event+0xcd/0x120 [ 38.437455][ T957] notifier_call_chain+0x90/0x160 [ 38.438067][ T957] netdev_change_features+0x74/0xa0 [ 38.438708][ T957] bond_compute_features.isra.45+0x4e6/0x6f0 [bonding] [ 38.439522][ T957] bond_enslave+0x3639/0x47b0 [bonding] [ 38.440225][ T957] do_setlink+0xaab/0x2ef0 [ 38.440786][ T957] __rtnl_newlink+0x9c5/0x1270 [ 38.441463][ T957] rtnl_newlink+0x65/0x90 [ 38.442075][ T957] rtnetlink_rcv_msg+0x4a8/0x890 [ 38.442774][ T957] netlink_rcv_skb+0x121/0x350 [ 38.443451][ T957] netlink_unicast+0x42e/0x610 [ 38.444282][ T957] netlink_sendmsg+0x65a/0xb90 [ 38.444992][ T957] ____sys_sendmsg+0x5ce/0x7a0 [ 38.445679][ T957] ___sys_sendmsg+0x10f/0x1b0 [ 38.446365][ T957] __sys_sendmsg+0xc6/0x150 [ 38.447007][ T957] do_syscall_64+0x99/0x4f0 [ 38.447668][ T957] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 38.448538][ T957] [ 38.448538][ T957] -> #0 (&bond->stats_lock_key#2){+.+.}: [ 38.449554][ T957] __lock_acquire+0x2d8d/0x3de0 [ 38.450148][ T957] lock_acquire+0x164/0x3b0 [ 38.450711][ T957] _raw_spin_lock+0x30/0x70 [ 38.451292][ T957] bond_get_stats+0x90/0x4d0 [bonding] [ 38.451950][ T957] dev_get_stats+0x1ec/0x270 [ 38.452425][ T957] bond_get_stats+0x1a5/0x4d0 [bonding] [ 38.453362][ T957] dev_get_stats+0x1ec/0x270 [ 38.453825][ T957] rtnl_fill_stats+0x44/0xbe0 [ 38.454390][ T957] rtnl_fill_ifinfo+0xeb2/0x3720 [ 38.456257][ T957] rtmsg_ifinfo_build_skb+0xca/0x170 [ 38.456998][ T957] rtmsg_ifinfo_event.part.33+0x1b/0xb0 [ 38.459351][ T957] rtnetlink_event+0xcd/0x120 [ 38.460086][ T957] notifier_call_chain+0x90/0x160 [ 38.460829][ T957] netdev_change_features+0x74/0xa0 [ 38.461752][ T957] bond_compute_features.isra.45+0x4e6/0x6f0 [bonding] [ 38.462705][ T957] bond_enslave+0x3639/0x47b0 [bonding] [ 38.463476][ T957] do_setlink+0xaab/0x2ef0 [ 38.464141][ T957] __rtnl_newlink+0x9c5/0x1270 [ 38.464897][ T957] rtnl_newlink+0x65/0x90 [ 38.465522][ T957] rtnetlink_rcv_msg+0x4a8/0x890 [ 38.466215][ T957] netlink_rcv_skb+0x121/0x350 [ 38.466895][ T957] netlink_unicast+0x42e/0x610 [ 38.467583][ T957] netlink_sendmsg+0x65a/0xb90 [ 38.468285][ T957] ____sys_sendmsg+0x5ce/0x7a0 [ 38.469202][ T957] ___sys_sendmsg+0x10f/0x1b0 [ 38.469884][ T957] __sys_sendmsg+0xc6/0x150 [ 38.470587][ T957] do_syscall_64+0x99/0x4f0 [ 38.471245][ T957] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 38.472093][ T957] [ 38.472093][ T957] other info that might help us debug this: [ 38.472093][ T957] [ 38.473438][ T957] Possible unsafe locking scenario: [ 38.473438][ T957] [ 38.474898][ T957] CPU0 CPU1 [ 38.476234][ T957] ---- ---- [ 38.480171][ T957] lock(&bond->stats_lock_key); [ 38.480808][ T957] lock(&bond->stats_lock_key#2); [ 38.481791][ T957] lock(&bond->stats_lock_key); [ 38.482754][ T957] lock(&bond->stats_lock_key#2); [ 38.483416][ T957] [ 38.483416][ T957] *** DEADLOCK *** [ 38.483416][ T957] [ 38.484505][ T957] 3 locks held by ip/957: [ 38.485048][ T957] #0: ffffffffbccf6230 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x457/0x890 [ 38.486198][ T957] #1: ffff888065fd2cd8 (&bond->stats_lock_key){+.+.}, at: bond_get_stats+0x90/0x4d0 [bonding] [ 38.487625][ T957] #2: ffffffffbc9254c0 (rcu_read_lock){....}, at: bond_get_stats+0x5/0x4d0 [bonding] [ 38.488897][ T957] [ 38.488897][ T957] stack backtrace: [ 38.489646][ T957] CPU: 1 PID: 957 Comm: ip Not tainted 5.5.0+ torvalds#394 [ 38.490497][ T957] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 [ 38.492810][ T957] Call Trace: [ 38.493219][ T957] dump_stack+0x96/0xdb [ 38.493709][ T957] check_noncircular+0x371/0x450 [ 38.494344][ T957] ? lookup_address+0x60/0x60 [ 38.494923][ T957] ? print_circular_bug.isra.35+0x310/0x310 [ 38.495699][ T957] ? hlock_class+0x130/0x130 [ 38.496334][ T957] ? __lock_acquire+0x2d8d/0x3de0 [ 38.496979][ T957] __lock_acquire+0x2d8d/0x3de0 [ 38.497607][ T957] ? register_lock_class+0x14d0/0x14d0 [ 38.498333][ T957] ? check_chain_key+0x236/0x5d0 [ 38.499003][ T957] lock_acquire+0x164/0x3b0 [ 38.499800][ T957] ? bond_get_stats+0x90/0x4d0 [bonding] [ 38.500706][ T957] _raw_spin_lock+0x30/0x70 [ 38.501435][ T957] ? bond_get_stats+0x90/0x4d0 [bonding] [ 38.502311][ T957] bond_get_stats+0x90/0x4d0 [bonding] [ ... ] But, there is another problem. The dynamic lockdep class key is protected by RTNL, but bond_get_stats() would be called outside of RTNL. So, it would use an invalid dynamic lockdep class key. In order to fix this issue, stats_lock uses spin_lock_nested() instead of a dynamic lockdep key. The bond_get_stats() calls bond_get_lowest_level_rcu() to get the correct nest level value, which will be used by spin_lock_nested(). The "dev->lower_level" indicates lower nest level value, but this value is invalid outside of RTNL. So, bond_get_lowest_level_rcu() returns valid lower nest level value in the RCU critical section. bond_get_lowest_level_rcu() will be work only when LOCKDEP is enabled. Fixes: 089bca2 ("bonding: use dynamic lockdep key instead of subclass") Signed-off-by: Taehee Yoo <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
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‎drivers/net/bonding/bond_main.c

Lines changed: 50 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -3436,18 +3436,65 @@ static void bond_fold_stats(struct rtnl_link_stats64 *_res,
34363436
}
34373437
}
34383438

3439+
#ifdef CONFIG_LOCKDEP
3440+
static int bond_get_lowest_level_rcu(struct net_device *dev)
3441+
{
3442+
struct net_device *ldev, *next, *now, *dev_stack[MAX_NEST_DEV + 1];
3443+
struct list_head *niter, *iter, *iter_stack[MAX_NEST_DEV + 1];
3444+
int cur = 0, max = 0;
3445+
3446+
now = dev;
3447+
iter = &dev->adj_list.lower;
3448+
3449+
while (1) {
3450+
next = NULL;
3451+
while (1) {
3452+
ldev = netdev_next_lower_dev_rcu(now, &iter);
3453+
if (!ldev)
3454+
break;
3455+
3456+
next = ldev;
3457+
niter = &ldev->adj_list.lower;
3458+
dev_stack[cur] = now;
3459+
iter_stack[cur++] = iter;
3460+
if (max <= cur)
3461+
max = cur;
3462+
break;
3463+
}
3464+
3465+
if (!next) {
3466+
if (!cur)
3467+
return max;
3468+
next = dev_stack[--cur];
3469+
niter = iter_stack[cur];
3470+
}
3471+
3472+
now = next;
3473+
iter = niter;
3474+
}
3475+
3476+
return max;
3477+
}
3478+
#endif
3479+
34393480
static void bond_get_stats(struct net_device *bond_dev,
34403481
struct rtnl_link_stats64 *stats)
34413482
{
34423483
struct bonding *bond = netdev_priv(bond_dev);
34433484
struct rtnl_link_stats64 temp;
34443485
struct list_head *iter;
34453486
struct slave *slave;
3487+
int nest_level = 0;
34463488

3447-
spin_lock(&bond->stats_lock);
3448-
memcpy(stats, &bond->bond_stats, sizeof(*stats));
34493489

34503490
rcu_read_lock();
3491+
#ifdef CONFIG_LOCKDEP
3492+
nest_level = bond_get_lowest_level_rcu(bond_dev);
3493+
#endif
3494+
3495+
spin_lock_nested(&bond->stats_lock, nest_level);
3496+
memcpy(stats, &bond->bond_stats, sizeof(*stats));
3497+
34513498
bond_for_each_slave_rcu(bond, slave, iter) {
34523499
const struct rtnl_link_stats64 *new =
34533500
dev_get_stats(slave->dev, &temp);
@@ -3457,10 +3504,10 @@ static void bond_get_stats(struct net_device *bond_dev,
34573504
/* save off the slave stats for the next run */
34583505
memcpy(&slave->slave_stats, new, sizeof(*new));
34593506
}
3460-
rcu_read_unlock();
34613507

34623508
memcpy(&bond->bond_stats, stats, sizeof(*stats));
34633509
spin_unlock(&bond->stats_lock);
3510+
rcu_read_unlock();
34643511
}
34653512

34663513
static int bond_do_ioctl(struct net_device *bond_dev, struct ifreq *ifr, int cmd)

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