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From: Nixiaoming <nixiaoming@huawei.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: "adobriyan@gmail.com" <adobriyan@gmail.com>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
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	"Huangjianhui (Alex)" <alex.huangjianhui@huawei.com>,
	Dailei <dylix.dailei@huawei.com>,
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Subject: RE: [PATCH v3 0/3] kernel/notifier.c: avoid duplicate registration
Date: Thu, 11 Jul 2019 01:32:57 +0000
Message-ID: <E490CD805F7529488761C40FD9D26EF12AC9D039@dggemm507-mbx.china.huawei.com> (raw)
In-Reply-To: <20190710055628.GB5778@kroah.com>

On Wed, July 10, 2019 1:56 PM Greg KH wrote:
>On Wed, Jul 10, 2019 at 11:09:07AM +0800, Xiaoming Ni wrote:
>> Registering the same notifier to a hook repeatedly can cause the hook
>> list to form a ring or lose other members of the list.
>
>Then don't do that :)
>

Duplicate registration is checked and exited in notifier_chain_cond_register()

Duplicate registration was checked in notifier_chain_register() but only 
the alarm was triggered without exiting. added by commit 831246570d34692e 
("kernel/notifier.c: double register detection")

This patch is similar to commit 8312465 and notifier_chain_cond_register(),
 with actual prevention for such behaviour,  which I think is necessary to 
 avoid the formation of a linked list ring.

>Is there any in-kernel users that do do this?  If so, please just fix
>them.
>
Notifier_chain_register() is not a hotspot path.
Adding a check here can make the kernel more stable.

Thanks

Xiaoming Ni


>thanks,
>
>greg k-h
>

      reply index

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

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