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* [PATCH v3 0/3] kernel/notifier.c: avoid duplicate registration
@ 2019-07-10  3:09 Xiaoming Ni
  2019-07-10  5:49 ` Vasily Averin
  2019-07-10  5:56 ` Greg KH
  0 siblings, 2 replies; 15+ messages in thread
From: Xiaoming Ni @ 2019-07-10  3:09 UTC (permalink / raw)
  To: adobriyan, akpm, anna.schumaker, arjan, bfields, chuck.lever,
	davem, gregkh, jlayton, luto, mingo, Nadia.Derbey, paulmck,
	semen.protsenko, stable, stern, tglx, torvalds, trond.myklebust,
	viresh.kumar, vvs
  Cc: alex.huangjianhui, dylix.dailei, nixiaoming, linux-kernel,
	linux-nfs, netdev

Registering the same notifier to a hook repeatedly can cause the hook
list to form a ring or lose other members of the list.

case1: An infinite loop in notifier_chain_register() can cause soft lockup
        atomic_notifier_chain_register(&test_notifier_list, &test1);
        atomic_notifier_chain_register(&test_notifier_list, &test1);
        atomic_notifier_chain_register(&test_notifier_list, &test2);

case2: An infinite loop in notifier_chain_register() can cause soft lockup
        atomic_notifier_chain_register(&test_notifier_list, &test1);
        atomic_notifier_chain_register(&test_notifier_list, &test1);
        atomic_notifier_call_chain(&test_notifier_list, 0, NULL);

case3: lose other hook test2
        atomic_notifier_chain_register(&test_notifier_list, &test1);
        atomic_notifier_chain_register(&test_notifier_list, &test2);
        atomic_notifier_chain_register(&test_notifier_list, &test1);

case4: Unregister returns 0, but the hook is still in the linked list,
        and it is not really registered. If you call notifier_call_chain
        after ko is unloaded, it will trigger oops. if the system is
       	configured with softlockup_panic and the same hook is repeatedly
       	registered on the panic_notifier_list, it will cause a loop panic.

so. need add a check in in notifier_chain_register() to avoid duplicate
registration

v1:
* use notifier_chain_cond_register replace notifier_chain_register

v2:
* Add a check in notifier_chain_register() to avoid duplicate registration
* remove notifier_chain_cond_register() to avoid duplicate code 
* remove blocking_notifier_chain_cond_register() to avoid duplicate code

v3:
* Add a cover letter.

Xiaoming Ni (3):
  kernel/notifier.c: avoid duplicate registration
  kernel/notifier.c: remove notifier_chain_cond_register()
  kernel/notifier.c: remove blocking_notifier_chain_cond_register()

 include/linux/notifier.h |  4 ----
 kernel/notifier.c        | 41 +++--------------------------------------
 net/sunrpc/rpc_pipe.c    |  2 +-
 3 files changed, 4 insertions(+), 43 deletions(-)

-- 
1.8.5.6


^ permalink raw reply	[flat|nested] 15+ messages in thread

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Thread overview: 15+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-10  3:09 [PATCH v3 0/3] kernel/notifier.c: avoid duplicate registration Xiaoming Ni
2019-07-10  5:49 ` Vasily Averin
2019-07-11  1:55   ` Nixiaoming
2019-07-11 13:57     ` Vasily Averin
2019-07-12 13:11       ` Xiaoming Ni
2019-07-12 14:07         ` gregkh
2019-07-14  2:45           ` Xiaoming Ni
2019-07-15  5:38             ` Vasily Averin
2019-07-16  2:00               ` Xiaoming Ni
2019-07-16 10:20                 ` Vasily Averin
2019-07-16 14:07                   ` Xiaoming Ni
2019-07-17 11:15                     ` Vasily Averin
2019-09-10  3:57                       ` Xiaoming Ni
2019-07-10  5:56 ` Greg KH
2019-07-11  1:32   ` Nixiaoming

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