Commit b3e80d44 authored by Taehee Yoo's avatar Taehee Yoo Committed by David S. Miller

bonding: fix lockdep warning in bond_get_stats()

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+ #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+ #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: 089bca2c ("bonding: use dynamic lockdep key instead of subclass")
Signed-off-by: default avatarTaehee Yoo <ap420073@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7151affe
...@@ -3526,6 +3526,47 @@ static void bond_fold_stats(struct rtnl_link_stats64 *_res, ...@@ -3526,6 +3526,47 @@ static void bond_fold_stats(struct rtnl_link_stats64 *_res,
} }
} }
#ifdef CONFIG_LOCKDEP
static int bond_get_lowest_level_rcu(struct net_device *dev)
{
struct net_device *ldev, *next, *now, *dev_stack[MAX_NEST_DEV + 1];
struct list_head *niter, *iter, *iter_stack[MAX_NEST_DEV + 1];
int cur = 0, max = 0;
now = dev;
iter = &dev->adj_list.lower;
while (1) {
next = NULL;
while (1) {
ldev = netdev_next_lower_dev_rcu(now, &iter);
if (!ldev)
break;
next = ldev;
niter = &ldev->adj_list.lower;
dev_stack[cur] = now;
iter_stack[cur++] = iter;
if (max <= cur)
max = cur;
break;
}
if (!next) {
if (!cur)
return max;
next = dev_stack[--cur];
niter = iter_stack[cur];
}
now = next;
iter = niter;
}
return max;
}
#endif
static void bond_get_stats(struct net_device *bond_dev, static void bond_get_stats(struct net_device *bond_dev,
struct rtnl_link_stats64 *stats) struct rtnl_link_stats64 *stats)
{ {
...@@ -3533,11 +3574,17 @@ static void bond_get_stats(struct net_device *bond_dev, ...@@ -3533,11 +3574,17 @@ static void bond_get_stats(struct net_device *bond_dev,
struct rtnl_link_stats64 temp; struct rtnl_link_stats64 temp;
struct list_head *iter; struct list_head *iter;
struct slave *slave; struct slave *slave;
int nest_level = 0;
spin_lock(&bond->stats_lock);
memcpy(stats, &bond->bond_stats, sizeof(*stats));
rcu_read_lock(); rcu_read_lock();
#ifdef CONFIG_LOCKDEP
nest_level = bond_get_lowest_level_rcu(bond_dev);
#endif
spin_lock_nested(&bond->stats_lock, nest_level);
memcpy(stats, &bond->bond_stats, sizeof(*stats));
bond_for_each_slave_rcu(bond, slave, iter) { bond_for_each_slave_rcu(bond, slave, iter) {
const struct rtnl_link_stats64 *new = const struct rtnl_link_stats64 *new =
dev_get_stats(slave->dev, &temp); dev_get_stats(slave->dev, &temp);
...@@ -3547,10 +3594,10 @@ static void bond_get_stats(struct net_device *bond_dev, ...@@ -3547,10 +3594,10 @@ static void bond_get_stats(struct net_device *bond_dev,
/* save off the slave stats for the next run */ /* save off the slave stats for the next run */
memcpy(&slave->slave_stats, new, sizeof(*new)); memcpy(&slave->slave_stats, new, sizeof(*new));
} }
rcu_read_unlock();
memcpy(&bond->bond_stats, stats, sizeof(*stats)); memcpy(&bond->bond_stats, stats, sizeof(*stats));
spin_unlock(&bond->stats_lock); spin_unlock(&bond->stats_lock);
rcu_read_unlock();
} }
static int bond_do_ioctl(struct net_device *bond_dev, struct ifreq *ifr, int cmd) static int bond_do_ioctl(struct net_device *bond_dev, struct ifreq *ifr, int cmd)
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment