diff options
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/batman-adv | |
parent | 44c23d71599f81a1c7fe8389e0319822dd50c37c (diff) |
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/batman-adv')
0 files changed, 0 insertions, 0 deletions