netdev - Re: [PATCH] inet_diag: make config INET

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Message-ID: <50603355.4010001@cn.fujitsu.com>
Date:	Mon, 24 Sep 2012 18:17:57 +0800
From:	Gao feng <gaofeng@...fujitsu.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Jan Engelhardt <jengelh@...i.de>,
	Stephen Hemminger <stephen.hemminger@...tta.com>,
	netdev@...r.kernel.org, davem@...emloft.net, kuznet@....inr.ac.ru
Subject: Re: [PATCH] inet_diag: make config INET_DIAG bool

于 2012年09月24日 17:42, Eric Dumazet 写道:
> In fact I didnt fully understand the problem you try to address.
> 
> If you want to prevent module being unloaded, you need to add proper
> module_get()/module_put()
> 
> So I would add a "struct module *module;" in struct sock_diag_handler
> and use it appropriately.

Yes, I try to add reference of the module,but I can't find a proper
location to call module_get and module_put.

module_get should be called when userspace program use netlink to
send dump request to the kernel,and module_put should be called when
the dump is completed. I am right?

BUT the userspace program may only call netlink_sendmsg without call
netlink_recvmsg.so the reference of the module will be incorrect.

> 
> But then, I might have totally misunderstood the problem.
> 
> Care to explain how you trigger the bug ?

It's very easy to trigger this bug,
you can exec "while :; do ss -a ; done" in one terminal
and exec "while :; do rmmod tcp_diag && rmmod inet_diag; done"
in another terminal.

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