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| author |   Cong Wang <xiyou.wangcong@gmail.com> | 2020-01-15 13:02:38 -0800 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2020-01-17 11:02:44 +0100 |
| commit | 53d374979ef147ab51f5d632dfe20b14aebeccd0 (patch) | |
| tree | 8eff9015b047aea4024a5b23a40b13c646b42b3d /net | |
| parent | net/sched: act_ife: initalize ife->metalist earlier (diff) | |
| download | linux-dev-53d374979ef147ab51f5d632dfe20b14aebeccd0.tar.xz linux-dev-53d374979ef147ab51f5d632dfe20b14aebeccd0.zip | |
net: avoid updating qdisc_xmit_lock_key in netdev_update_lockdep_key()
syzbot reported some bogus lockdep warnings, for example bad unlock
balance in sch_direct_xmit(). They are due to a race condition between
slow path and fast path, that is qdisc_xmit_lock_key gets re-registered
in netdev_update_lockdep_key() on slow path, while we could still
acquire the queue->_xmit_lock on fast path in this small window:
CPU A CPU B
__netif_tx_lock();
lockdep_unregister_key(qdisc_xmit_lock_key);
__netif_tx_unlock();
lockdep_register_key(qdisc_xmit_lock_key);
In fact, unlike the addr_list_lock which has to be reordered when
the master/slave device relationship changes, queue->_xmit_lock is
only acquired on fast path and only when NETIF_F_LLTX is not set,
so there is likely no nested locking for it.
Therefore, we can just get rid of re-registration of
qdisc_xmit_lock_key.
Reported-by: syzbot+4ec99438ed7450da6272@syzkaller.appspotmail.com
Fixes: ab92d68fc22f ("net: core: add generic lockdep keys")
Cc: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/dev.c | 12 |
1 files changed, 0 insertions, 12 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index 0ad39c87b7fd..7e885d069707 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -9177,22 +9177,10 @@ static void netdev_unregister_lockdep_key(struct net_device *dev) void netdev_update_lockdep_key(struct net_device *dev) { - struct netdev_queue *queue; - int i; - - lockdep_unregister_key(&dev->qdisc_xmit_lock_key); lockdep_unregister_key(&dev->addr_list_lock_key); - - lockdep_register_key(&dev->qdisc_xmit_lock_key); lockdep_register_key(&dev->addr_list_lock_key); lockdep_set_class(&dev->addr_list_lock, &dev->addr_list_lock_key); - for (i = 0; i < dev->num_tx_queues; i++) { - queue = netdev_get_tx_queue(dev, i); - - lockdep_set_class(&queue->_xmit_lock, - &dev->qdisc_xmit_lock_key); - } } EXPORT_SYMBOL(netdev_update_lockdep_key); |