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From: Xiaoming Ni <nixiaoming@huawei.com>
To: <adobriyan@gmail.com>, <akpm@linux-foundation.org>,
	<anna.schumaker@netapp.com>, <arjan@linux.intel.com>,
	<bfields@fieldses.org>, <chuck.lever@oracle.com>,
	<davem@davemloft.net>, <gregkh@linuxfoundation.org>,
	<jlayton@kernel.org>, <luto@kernel.org>, <mingo@kernel.org>,
	<Nadia.Derbey@bull.net>, <paulmck@linux.vnet.ibm.com>,
	<semen.protsenko@linaro.org>, <stable@kernel.org>,
	<stern@rowland.harvard.edu>, <tglx@linutronix.de>,
	<torvalds@linux-foundation.org>,
	<trond.myklebust@hammerspace.com>, <viresh.kumar@linaro.org>,
	<vvs@virtuozzo.com>
Cc: <alex.huangjianhui@huawei.com>, <dylix.dailei@huawei.com>,
	<nixiaoming@huawei.com>, <linux-kernel@vger.kernel.org>,
	<linux-nfs@vger.kernel.org>, <netdev@vger.kernel.org>
Subject: [PATCH v3 0/3] kernel/notifier.c: avoid duplicate registration
Date: Wed, 10 Jul 2019 11:09:07 +0800
Message-ID: <1562728147-30251-1-git-send-email-nixiaoming@huawei.com> (raw)

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


             reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-10  3:09 Xiaoming Ni [this message]
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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