https://github.com/torvalds/linux
Revision 53d374979ef147ab51f5d632dfe20b14aebeccd0 authored by Cong Wang on 15 January 2020, 21:02:38 UTC, committed by David S. Miller on 17 January 2020, 10:02:44 UTC
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>
1 parent 44c23d7
Tip revision: 53d374979ef147ab51f5d632dfe20b14aebeccd0 authored by Cong Wang on 15 January 2020, 21:02:38 UTC
net: avoid updating qdisc_xmit_lock_key in netdev_update_lockdep_key()
net: avoid updating qdisc_xmit_lock_key in netdev_update_lockdep_key()
Tip revision: 53d3749
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| .clang-format | -rw-r--r-- | 15.0 KB |
| .cocciconfig | -rw-r--r-- | 59 bytes |
| .get_maintainer.ignore | -rw-r--r-- | 71 bytes |
| .gitattributes | -rw-r--r-- | 62 bytes |
| .gitignore | -rw-r--r-- | 1.7 KB |
| .mailmap | -rw-r--r-- | 14.1 KB |
| COPYING | -rw-r--r-- | 423 bytes |
| CREDITS | -rw-r--r-- | 97.3 KB |
| Kbuild | -rw-r--r-- | 1.3 KB |
| Kconfig | -rw-r--r-- | 595 bytes |
| MAINTAINERS | -rw-r--r-- | 526.6 KB |
| Makefile | -rw-r--r-- | 59.4 KB |
| README | -rw-r--r-- | 727 bytes |
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